ANALYSIS OF ALTERNATIVES NON-CONFIDENTIAL VERSION

ANALYSIS OF ALTERNATIVES

NON-CONFIDENTIAL VERSION

Legal name of applicant(s): H&R Ölwerke Schindler GmbH

H&R Chemisch Pharmazeutische Spezialitäten GmbH

(co-applicant)

Submitted by: H&R Ölwerke Schindler GmbH

Substance: Sodium dichromate

CAS No. 10588-01-9 (anhydrous)

CAS No. 7789-12-0 (dihydrate)

EC No. 234-190-3

Use title: Use of sodium dichromate as corrosion inhibitor in

ammonia absorption deep cooling systems, applied for

the dewaxing and deoiling process steps of petroleum

raffinate.

Use number: 1


Use number: 1 H&R Ölwerke Schindler GmbH, H&R Chemisch Pharmazeutische Spezialitäten GmbH

2

CONTENTS

LIST OF TABLES ........................................................................................................................................................ 4

LIST OF FIGURES ...................................................................................................................................................... 4

LIST OF ABBREVIATIONS ....................................................................................................................................... 5

GLOSSARY ................................................................................................................................................................. 6

DECLARATION .......................................................................................................................................................... 7

IMPORTANT POINTS ON THE IDENTITIES OF KEY STAKEHOLDERS ........................................................... 8

1. SUMMARY ............................................................................................................................................................ 9

2. INTRODUCTION .................................................................................................................................................. 13

2.1 Substance ........................................................................................................................................................ 13 2.1.1 Chemical and physicochemical properties .......................................................................................... 13 2.1.2 Toxicological characteristics ............................................................................................................... 14

2.2 Purpose and benefits of sodium dichromate as corrosion inhibitor ................................................................ 15

3. ANALYSIS OF SUBSTANCE FUNCTION.......................................................................................................... 16

3.1 The role of the AADC systems in the production of base oil and waxes........................................................ 16 3.1.1 Overview of the process ...................................................................................................................... 16 3.1.2 Dewaxing and deoiling ........................................................................................................................ 18

3.2 Industrial AADC systems ............................................................................................................................... 19 3.2.1 Properties and general parameters ....................................................................................................... 19 3.2.2 H&R’s AADC systems in Hamburg and Salzbergen (Germany) ........................................................ 21

3.3 Corrosion and corrosion inhibition in AADC systems ................................................................................... 24 3.3.1 General remarks on corrosion ............................................................................................................. 24 3.3.2 Consequences of the absence of corrosion inhibitors .......................................................................... 25 3.3.3 Corrosion inhibition with sodium dichromate ..................................................................................... 25

4. ANNUAL TONNAGE............................................................................................................................................ 29

5. IDENTIFICATION AND IMPLEMENTATION OF POSSIBLE ALTERNATIVES .......................................... 30

5.1 Description of efforts made to identify possible alternatives .......................................................................... 30 5.1.1 Research and development activities ................................................................................................... 30 5.1.2 Consultations and directed communications ....................................................................................... 30

5.2 Overview on the process of alternative development and industrial implementation..................................... 32

5.3 List of possible alternatives ............................................................................................................................ 35

6. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES FOR THE AADC SYSTEMS OF

H&R ............................................................................................................................................................................. 36

6.1 Alternative 1: Replacement (change) of the cooling system .......................................................................... 36



3

6.1.1 Properties/Description ......................................................................................................................... 36 6.1.2 Technical feasibility ............................................................................................................................ 36 6.1.3 Economic feasibility ............................................................................................................................ 37 6.1.4 Reduction of overall risk due to transition to the alternative ............................................................... 38 6.1.5 Availability .......................................................................................................................................... 39 6.1.6 Conclusion on suitability and availability ........................................................................................... 39

6.2 Alternative 2: Replacement of corrosion prone parts ..................................................................................... 39 6.2.1 Properties/Description ......................................................................................................................... 39 6.2.2 Technical feasibility ............................................................................................................................ 39 6.2.3 Economic feasibility ............................................................................................................................ 40 6.2.4 Reduction of overall risk ..................................................................................................................... 42 6.2.5 Availability .......................................................................................................................................... 42 6.2.6 Conclusion ........................................................................................................................................... 42

6.3 Alternative 3: Substitution of sodium dichromate as corrosion inhibitor ....................................................... 42 6.3.1 Technical requirements for corrosion inhibitors at the applicants sites ............................................... 43 6.3.2 Assessment of alternative corrosion protective substances: Category 1 .............................................. 44 6.3.2.1 Molybdate compounds ........................................................................................................................ 44 6.3.2.2 Sodium nitrite ...................................................................................................................................... 46 6.3.2.3 Silicates/water glass ............................................................................................................................ 49 6.3.2.4 Zinc containing corrosion inhibitors.................................................................................................... 51 6.3.2.5 Strong alkaline solutions ..................................................................................................................... 54 6.3.2.6 Phosphates and phosphonate compounds ............................................................................................ 56 6.3.2.7 Rare Earth Metal Salts ......................................................................................................................... 59

7. OVERALL CONCLUSION ON SUITABILITY AND AVAILABILITY OF CORROSION INHIBITOR

ALTERNATIVES ........................................................................................................................................................ 61

8. REFERENCES........................................................................................................................................................ 63

APPENDICES .............................................................................................................................................................. 67

Appendix 1 - Category 2 alternatives ...................................................................................................................... 67

Appendix 2 – Information on chemical substances assessed in Section 6.3 ........................................................... 74



4

LIST OF TABLES

Table 1: Summary of alternative evaluation. Red area: the parameters/assessment criteria do not fulfil the requirements

Yellow area: the parameters/assessment criteria fulfilment is not yet clear Green area: the parameters/assessment

criteria do fulfil the requirements White area: no data available .................................................................................. 11 Table 2: Substance subject to this AoA. ...................................................................................................................... 13 Table 3: Physical and chemical characteristics of sodium dichromate ........................................................................ 14 Table 4: Harmonized classification of sodium dichromate .......................................................................................... 14 Table 5: Example products made from base oil, slack wax, foots oil and paraffin ...................................................... 16 Table 6: Important parameters and functionalities of sodium dichromate as corrosion inhibitor ................................ 26 Table 7: Categorized list of alternative corrosion inhibitors ........................................................................................ 35 Table 8: Advantages of the two cooling technologies ................................................................................................. 37 Table 9: Net Economic Impacts – replacement (change) of the cooling system ......................................................... 38 Table 10: Net Economic Impacts – replacement of corrosion prone parts .................................................................. 41

LIST OF FIGURES

Figure 1: Expected timeframe of sodium dichromate substitution in the AADC systems in Hamburg and Salzbergen

(Germany) ..................................................................................................................................................................... 12 Figure 2: Broad overview of operations of the applicants: Base oil and wax production. ATM = Atmospheric Residue,

VGO = Vacuum Gas Oil, DAO= De-Asphalted Oil ..................................................................................................... 17 Figure 3: Generic overview of operations in Salzbergen (above) and Hamburg (below). While the operations in

Salzbergen comprise de-waxing with integrated deoiling, the operations in Hamburg comprise dewaxing only. ....... 17 Figure 4: Photographs of feedstock and products: Dewaxing: feedstock (raffinate, left), base oil product (middle), and

slack wax (right) ........................................................................................................................................................... 18 Figure 5: Photographs of feedstock and products: Combined Dewaxing and Deoiling: feedstock (raffinate, far left),

base oil product (second left), hard paraffin wax (second right), foots oil (far right) ................................................... 19 Figure 6: Simplified functional scheme of an AADC system ..................................................................................... 20 Figure 7: H&R’s AADC system in Salzbergen (Germany). ........................................................................................ 23 Figure 8: Expected timeframe of sodium dichromate substitution in the AADC systems in Hamburg and Salzbergen

(Germany) ..................................................................................................................................................................... 34



5

LIST OF ABBREVIATIONS

AADC Ammonia Absorption Deep Cooling

AfA Application for Authorisation

AoA Analysis of Alternatives

AC Alternating Current

bar(a) Unit for absolute pressure

Cr(VI) Hexavalent Chromium

CSR Chemical Safety Report

DMEA N,N′-Dimethylethanolamine

EC European Commission

ECHA European Chemicals Agency

EPO European Patent Office

EU European Union

H2 Hydrogen

HPA Hydroxy Phosphonic Acid

IE (Corrosion) Inhibition Efficiency

MSG Mono Sodium Glutamate

MTI Materials Technology Institute

MW Megawatt

N2 Nitrogen

Na2Cr2O7 Sodium dichromate

NPV Net Present Value

NUS Non Use Scenario

O2 Oxygen

R&D Research and Development

RAC Committee of Risk Assessment

REACH Registration, Evaluation, Authorisation and Restriction of Chemicals

SEA Socio-Economic Analysis

SVHC Substance of Very High Concern

TSP Trisodium Phosphate

US United States

VCC Vapour Compression Cooling

W Watt



6

GLOSSARY

Term Definition

Category 1 alternative

Initial R&D efforts on ammonia water based absorption systems

can be found. Although partly tested on test vessels or

commercially available small scale units, they are far away from

being applied on the industrial scale. Respective R&D is mostly

of basic nature than ongoing.

Category 2 alternative

Only indications for the use as corrosion inhibitor for carbon

steel was found in the course of the literature review. Results are

restricted to the laboratory scale and no indication for the use in

ammonia water based absorption systems is present. In addition,

Category 2 alternatives exhibit technical limitations leading to

dismissal.

Corrosion protection Means applied to the metal surface to prevent or interrupt

oxidation of the metal part leading to loss of material.

Industrial scale Large cooling systems with capacities of >2 MW for industrial

applications such as chemical synthesis, refineries etc.

Risk reduction

Classification and labelling information of substances and

products reported during the consultation being used for

alternatives / alternative processes are compared to the hazard

profile of the used sodium dichromate

Rich solution Aqueous ammonia solution with high ammonia content (approx.

26 %).

Small scale

Commercially available ammonia water (cooling) systems for

household applications such as refrigerator, medical boxes, air

conditioning etc. with capacities of several hundred Watts.

Test vessel

Test system typically made of carbon steel that can be brought to

similar temperature and pressure as at the critical points of an

absorption cycle.

Most of the effectiveness tests on alternative corrosion inhibitors

are performed in vessels measuring the amount of corrosion

gases and finally analyses the sample surface. Simulation vessels

are used for cost reasons, so that an entire machine incorporating

an absorption cycle does not have to be used, often for thousands

of hours, at each test on a new corrosion inhibitor.

Poor solution Aqueous ammonia solution with low ammonia content (approx.

11-12 %)



8

IMPORTANT POINTS ON THE IDENTITIES OF KEY STAKEHOLDERS

H&R GmbH & Co. KGaA: H&R GmbH & Co. KGaA (H&R KGaA) is a holding company

which owns (partially or wholly) several subsidiaries based around the globe which would be

affected by a refused authorisation. Among those, those more important to this analysis are the

two companies who own the two refineries that use sodium dichromate (see below).

The two refineries: At the core of H&R KGaA are two refineries, both located in Germany, one

in Hamburg and another one in Salzbergen. The Hamburg refinery is owned and operated by

H&R Ölwerke Schindler GmbH (H&R OWS), while the Salzbergen refinery is owned and

operated by H&R Chemisch Pharmazeutische Spezialitäten GmbH (H&R CPS). These two

companies are the applicants for this joint Application for Authorisation and are collectively

referred to as such throughout this document.

Hansen & Rosenthal Group: The Hansen & Rosenthal Group owns xxx of H&R KGaA and

acts as selling partner directly linked to the two refineries. Four such companies are offering

marketing and sales services, all based in Germany:

Hansen & Rosenthal KG

Klaus Dahleke KG

Tudapetrol Nils Hansen Mineralölerzeugnisse KG

H&R Wax & Specialties GmbH



9

1. SUMMARY

Use of sodium dichromate by the applicants:

This Analysis of Alternatives (AoA) forms part of the Application for Authorisation (AfA) to

continue the use sodium dichromate as corrosion inhibitor in Ammonia Absorption Deep Cooling

(AADC) systems operated by the applicants H&R Ölwerke Schindler GmbH in their refinery in

Hamburg and H&R Chemisch Pharmazeutische Spezialitäten GmbH in their refinery in Salzbergen

(Germany). Both legal entities are part of H&R GmbH Co. KGaA and act as joint applicants.

The applicants use the AADC systems to generate cold, which is required for the process steps of

dewaxing and deoiling of raffinates to obtain base oil and waxes. Base oil and waxes serve as raw

materials for the production of various products such as lubricants, motor oil, candles, inks, electrical

insulation or composite wood panels. Sodium dichromate is used in the working fluid (ammonia water

mixture) of the AADC systems as an additive to inhibit corrosion of the carbon steel which the

systems are made of.

The annual tonnage is xxxxxxx (≤ 0.01 tonnes) sodium dichromate [xxxxx as Cr(VI)].

Important substance properties:

The following key functionalities are considered essential for the use of sodium dichromate as

corrosion inhibitor in AADC systems:

Corrosion protection for carbon steel in ammonia/water based systems by formation of a

passivation layer in the absence of oxygen;

Prevention of formation of non-condensable (inert) gases;

Active corrosion inhibition when a coating is damaged;

Inhibitor does not negatively influence the ammonia absorption refrigeration process;

Non-volatile corrosion inhibitor with proven long-term stability.

The AADC systems, which are designed as closed systems, operate at a broad temperature range (35

- 165 °C), different pressures, alkaline pH (9 - 12), high fluid velocities and under very low oxygen

levels. As of today, Cr(VI) based substances are the only proven corrosion inhibitors suitable for the

use under such conditions.

Alternative assessment:

Three different alternative options are discussed in this AoA:

Replacement (change) of the cooling system with a system making use of a different cooling

technology, e.g. Vapour Compression Cooling (VCC) (Section 6.1)

Replacement of corrosion prone parts with parts made of more resistant materials, e.g.

stainless steel (Section 6.2)

Substitution of sodium dichromate as corrosion inhibitor in existing AADC systems

(Section 6.3)



10

As a first option, the exchange of the existing AADC systems to an alternative cooling technology,

namely VCC, is described in Section 6.1. VCC systems are described to be operated without corrosion

inhibitor due to the absence of water and oxygen in completely closed systems. Even though

technically feasible, a switch to VCC would in H&R’s case amount to net economic impacts of

EUR 40 million (considering investment in a new cooling system, value added forgone due to

downtime and additional operational costs), which is why replacing the AADC systems with VCC

systems is not considered feasible from an economic standpoint.

As described in Section 6.2, the replacement of corrosion prone parts, mainly carbon steel parts by

more resistant parts, e.g. stainless steel or permanently coated metal parts, was also assessed for

suitability as alternative. As of today, no standard or best-practice solution is applicable for AADC

systems. It was highlighted that stainless steel systems of this size are currently not operated and no

reliable conclusion about the presence or absence of corrosion inhibitors in such systems can be

drawn. It was also clearly outlined that stainless steel is subject to corrosion in ammonia/water

systems, especially at higher temperatures. At present, no information exists on corrosion inhibition

for systems made of stainless steel. It is still questionable whether AADC systems in such dimensions

could be safely operated over the timeframe of decades without any corrosion inhibitor, despite the

use of stainless steel parts. It was also recommended by specialists that in this case only sodium

dichromate is proven for use as a long-term corrosion inhibitor. Therefore, from a technical

perspective, the exchange of corrosion prone parts cannot be considered as a suitable alternative.

In Section 6.3 the substitution of sodium dichromate by another corrosion inhibitor is described in

detail. Extensive efforts were made during the last years to identify possible alternatives for corrosion

inhibitors in AADC systems. In course of these efforts, scientific literature was screened and

evaluated comprehensively. Experts from other companies dealing with similar cooling systems were

approached. Moreover, several other international research institutes were contacted to discuss and

evaluate the state of the art for corrosion inhibition in these types of cooling systems. In summary,

this analysis revealed that there is limited experience available on replacement substances for large

scale industrial AADC systems. Despite all efforts, the current state of knowledge shows that a

technically feasible drop-in alternative to sodium dichromate for the use as corrosion inhibitor is not

available, neither for large scale industrial AADC systems nor for small scale applications. An

overview on the performance of the alternatives can be found in Table 1.



11

Table 1: Summary of alternative evaluation.

Red area: the parameters/assessment criteria do not fulfil the requirements.

Yellow area: the parameters/assessment criteria fulfilment is not yet clear.

Green area: the parameters/assessment criteria fulfil the requirements.

White area: no data available.

Expected time-scale of sodium dichromate substitution:

AADC systems made of carbon steel constitute a safe and reliable cooling technology. Using sodium

dichromate as corrosion inhibitor ensures a long-lasting life time of the cooling plants: up to 50 years.

Most alternatives discussed in scientific and technical literature were not tested under realistic

conditions in large-scaled systems for a realistic time span. For the development and industrial

upscaling of a possible alternative for sodium dichromate as a corrosion inhibitor for AADC systems

made of carbon steel, several phases are necessary. The integrity and reliability of the system must

be ensured over the expected lifetime of the facility. Unexpected corrosion would lead to system

downtime associated by immense costs and reduced environmental and occupational safety. In this

context, it would be unjustifiable to simply start a substitution in form of a field trial without having

enough scientific and empirical data about the safe use of such alternatives.

In Section 5.2 the expected timeline of a possible sodium chromate substitution process is described.

The substitution process can be divided into three phases: Research and Development (R&D), up-

scaling and implementation. The development process must start with a search for alternatives, which

has already been initiated with the development of this AfA. A literature-based analysis of possible

corrosion inhibitors and communications with experts was performed for the purpose of the AfA by

Arlanxeo Netherlands B.V., for which the applicants hold a letter of access.

The challenging issue in this context is evident in the fact that H&R is the operator but not the

manufacturer of the AADC systems, and the downstream user of sodium dichromate as a corrosion

inhibitor. H&R is aware of their responsibility as operator of AADC systems to contribute to the

investigation of all potential alternatives.

Alternative

Experience

at industrial

scale

Experience

at small

scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

35-165 °C

Effective at

alkaline pH

(9-12)

Effective in

absence of

oxygen

Molybdate

Sodium

nitrite

Silica/ water

glass

Silicates/

water glass

only

Silicates/

water glass

only

Silicates/

water glass

only

Zinc

compounds

Strong

alkaline

solutions

Phosphates

Rare earth

metal salts



12

Continuous monitoring of the robustness and reliability of the alternative is important to avoid any

failure of the replacement potentially causing severe consequences. In this context it is also of the

utmost importance to have the possibility to keep the system running in case the (technical or

chemical) alternative fails. For this purpose, the option to switch back to the use of sodium

dichromate must be available until a reliable solution is found.

As clearly outlined, passing Phase I and II will take up to 15 years. Assuming that initiatives will start

in 2017, it is anticipated that the process can easily take until 2032. The next maintenance window

for the connected production plant, which is accompanied by a temporary production stop, will also

take place in 2032 (five-year rhythm with the latest window in 2017). At least another five years are

required for performance monitoring, adding up the overall required time of 20 years. Besides this, it

must be considered that the remaining life time of the AADC systems operated by H&R is at least 35

years (Hamburg) and at least 20 years (Salzbergen). Therefore, these AADC systems are estimated

to be in use until 2037 and 2052 respectively (see Figure 1).

Figure 1: Expected timeframe of sodium dichromate substitution in the AADC systems in Hamburg and

Salzbergen (Germany)

All in all, passing the complete development and implementation process plus the required

monitoring will easily take 20 years. Taking into account the limited worker exposure to sodium

dichromate in combination with extremely high occupational safety measures (see CSR), the resulting

considerable low health impacts (under existing conditions there is no concern and negligible risk for

workers and the environment) and the comparably high economic impacts (see SEA), the most

reasonable option is to run the AADC systems operated by H&R until the end of their expected

lifetime (20 to 35 years from now). Therefore, H&R applies for a review period of 20 years for the

use of sodium dichromate.



13

2. INTRODUCTION

The present document constitutes the Analysis of Alternatives (AoA) as part of the Application for

Authorisation (AfA) to continue the use of sodium dichromate as corrosion inhibitor in Ammonia

Absorption Deep Cooling (AADC) systems operated by H&R Ölwerke Schindler GmbH in their

refinery in Hamburg and H&R Chemisch Pharmazeutische Spezialitäten GmbH in their refinery in

Salzbergen (Germany). In both cases the AADC system is critical for the dewaxing and deoiling of

raffinate to obtain base oil and waxes. Both legal entities are part of H&R GmbH Co. KGaA and act

as joint applicants. H&R Ölwerke Schindler GmbH and H&R Chemisch Pharmazeutische

Spezialitäten GmbH will be referred to in short as “H&R”.

The following Section 2.1 gives an overview of sodium dichromate and respective chemical and

physicochemical properties as well as toxicological characteristics. The purpose and benefits of using

sodium dichromate as corrosion inhibitor are introduced in Section 2.2.

H&R holds a Letter of Access (LoA) for the AfA Arlanxeo Netherlands B.V. filed in 2015 for the

use of sodium dichromate as corrosion inhibitor in ammonia absorption deep cooling systems. The

AfA was originally filed by Lanxess Elastomers B.V. before a legal entity change. It will be referred

to in short as “the Arlanxeo AfA”. Therefore the present AoA includes both, information from the

Arlanxeo AoA and information from H&R.

2.1 Substance

The following substance, as described in Table 2 is subject to this AoA.

Table 2: Substance subject to this AoA.

Substance Latest application date1 Sunset date2

Sodium dichromate (Na2Cr2O7)


CAS No. 7789-12-0 (dihydrate)

EC No. 234-190-3

21 March 2016 21 September 2017

1 Date referred to in Article 58(1)(c)(ii) of Regulation (EC) No. 1907/2006 2 Date referred to in Article 58(1)(c)(i) of Regulation (EC) No. 1907/2006

Sodium dichromate is an inorganic hexavalent chromium [Cr(VI)] salt, which has been identified as

Substance of Very High Concern (SVHC) and which has been included into Annex XIV to Regulation

(EC) No 1907/2006 ('REACH') due to its intrinsic properties as being carcinogenic (Carc. 1B),

mutagenic (Muta. 1B) and toxic to reproduction (Repr. 1B).

2.1.1 Chemical and physicochemical properties

Sodium dichromate is an odourless essentially non-volatile solid and appears as bright red-orange

crystal needles. Sodium dichromate is hygroscopic and very soluble in water and often found as

dihydrate. The aqueous solution of sodium dichromate is acidic and a strong oxidising agent. Physical

and chemical characteristics of sodium dichromate are summarized in Table 3.



14

Table 3: Physical and chemical characteristics of sodium dichromate

Parameter Value


7789-12-0 (dihydrate)

EC No. 234-190-3

Chemical formula Na2Cr2O7

Molecular weight 261.97 g/mol

Water solubility at 20°C ca. 2.355 g/L

Specific gravity 2.52 g/cm³

pH value at 25 °C and for a solution of

100 g/L 3.5

Melting point 356.7 °C

Boiling point (decomposition) > 400 °C

Physical state Odourless orange to red crystals or granules

Stability Stable under ordinary conditions

2.1.2 Toxicological characteristics

Cr(VI) compounds like sodium dichromate are known to induce multiple acute and chronic health

effects. Sodium dichromate is harmonized classified under Annex VI to Regulation (EC) No

1272/2008 (CLP Regulation), which is summarized in Table 4.

Table 4: Harmonized classification of sodium dichromate

Hazard Class and Category

Code(s)

Hazard Statement

Code(s) Pictograms

Ox. Sol. 2 H272

Acute Tox. 3 H301

Acute Tox. 4 H312

Skin Corr. 1B H314

Skin Sens. 1 H317

Acute Tox. 2 H330

Resp. Sens. 1 H334

Muta. 1B H340

Carc. 1B H350

Repr. 1B H360FD



15

Hazard Class and Category

Code(s)

Hazard Statement

Code(s) Pictograms

STOT RE 1 H372

Aquatic Acute 1 H400

Aquatic Chronic 1 H410

2.2 Purpose and benefits of sodium dichromate as corrosion inhibitor

Cr(VI) substances offer a broad range of functions which have been widely utilized for over 50 years

in the industry for various applications. The multi-functionality of Cr(VI) compounds provides major

properties within the respective processes. The following key functionalities are essential for the use

of sodium dichromate as corrosion inhibitor in AADC systems as they are subject of this AoA:

- Excellent corrosion protection and prevention for nearly all metals in a wide range of

environments;

- Proven technology for AADC systems – for application at high temperature in the desorber,

very low oxygen content, water rich material, high velocity;

- Effective at prevalent conditions; i.e. alkaline pH > 9, temperatures between 35–165 °C and

high liquid velocity;

- Prevention of formation of non-condensable (inert) gases;

- Formation of passivation layer in the absence of oxygen;

- Active corrosion inhibition when a coating is damaged, e.g. by a scratch exposing the base

material to the environment, the solubility properties of sodium dichromate enable them to

diffuse to the exposed area and inhibit corrosion;

- Inhibitor does not influence adsorption / desorption process;

- Product stability under the applied process conditions;

- Long-term stability of the corrosion inhibitor;

- No fouling/loose sedimentation products;

- Non-volatile; and

- Inhibits the growth of microorganisms in the cooling system

A detailed description of function of sodium dichromate is given in Chapter 3, including further

elaboration on key functionalities touched upon above in Section 3.3.



16

3. ANALYSIS OF SUBSTANCE FUNCTION

In order to be able to assess possible alternatives to sodium dichromate as corrosion inhibitor in

AADC systems, the following section provides background information on the industrial application

sodium dichromate is used in and properties, parameters as well as mechanisms which provide the

desired functioning.

Therefore, in Section 3.1 a general overview of the production process of base oil and waxes and the

special process step that involves the AADC systems is provided.

In Section 3.2 industrial uses of AADC systems, their properties and general parameters (3.2.1), as

well as the specific application at the H&R production sites in Hamburg and Salzbergen (Germany).

(3.2.2) are described.

Corrosion and its inhibition in AADC systems is further elaborated in Section 3.3, including a general

introduction to the issue of corrosion (3.3.1), resulting consequences (3.3.2) as well as the functioning

of sodium dichromate as corrosion inhibitor in AADC systems (3.3.3).

3.1 The role of the AADC systems in the production of base oil and waxes

3.1.1 Overview of the process

H&R produces base oil and waxes (slack wax, foots oil and paraffin) at the refineries in Hamburg

and Salzbergen (Germany). Both refineries process similar raw material (Vacuum Gas Oil,

Atmospheric Residue) with very similar main production steps (distillation, extraction,

dewaxing/deoiling and hydrofinishing). The AADC system is necessary to provide the required low

process temperature in the dewaxing/deoiling process step, from which base oil and waxes are

separated. From these raw materials more than 800 different specialty products are produced (see

Table 5 for examples). An effective dewaxing/deoiling step is essential for achieving product

specifications.

Table 5: Example products made from base oil, slack wax, foots oil and paraffin

Base oil lubricating greases, motor oil, metal processing fluids

Slack wax candles, polishes, matches, inks, carbon paper, canvass coatings, and composite

wood panels

Foots oil petroleum jelly, further refinement with e.g. hydro treatment

Hard paraffin

wax

lubrication, electrical insulation, candles, crayons

The purpose of dewaxing is to separate waxy components from oil products out of the extraction

plants to obtain a base oil with a low pour point. As a “side product” waxes are won, which also serve

as raw material for various applications (see Figure 2).



17

Figure 2: Broad overview of operations of the applicants: Base oil and wax production. ATM = Atmospheric

Residue, VGO = Vacuum Gas Oil, DAO= De-Asphalted Oil

The applicants have two dewaxing/deoiling units, which are supplied with cold by AADC systems.

One of these units is located in Salzbergen and is called “EP”. The unit is a 2-filtration-stage process

with a dewaxing stage and integrated deoiling stage (see Figure 3).

The other unit, called “EP2” is located in Hamburg and is used for a 1-filtration-stage process for

dewaxing only (see Figure 3).

The Hamburg and Salzbergen sites have similar processes, technical equipment and risk management

measures for dewaxing and deoiling activities. Therefore, all technical descriptions below are

common for the Hamburg and Salzbergen sites.

The units run continuously, except for scheduled stops as required by legislation, and as described in

the CSR to this application.

Figure 3: Generic overview of operations in Salzbergen (above) and Hamburg (below). While the operations

in Salzbergen comprise de-waxing with integrated deoiling, the operations in Hamburg comprise dewaxing only.

The cooling step is specifically essential for the dewaxing and deoiling process in order to achieve

the separation of the oil fraction from the wax fraction. This process step is discussed in detail in the



18

following section. For further information on products, markets, uses and the production process

please refer to the SEA document.

3.1.2 Dewaxing and deoiling

In the dewaxing step, the wax is separated from the base oil. Therefore, the raffinate (the feed) has to

be diluted with a selective solvent and chilled to a low temperature (-20 °C). By lowering the

temperature the waxy components begin to crystallise. The solid waxy crystals can then be removed

by filtration. The product emerging from this process is a base oil. It is ready for sale or further

processing (e.g. hydro-finishing). The other, waxy fraction that is won in the process is called slack

wax. It still contains some oil (typically 3 to 16 %).

In EP (Salzbergen) a second filtration step, the deoiling, is applied to further purify the waxy fraction

and win foots oil (a soft wax) and hard wax (paraffin). In the process step the temperature is increased

to melt the lower wax fractions, which are then separated from the higher wax fraction again by

filtration. However, the deoiling also takes place at low temperatures of 0 to +5 °C. Therefore cooling

is nevertheless important in order to keep the feed wax in a solid state and prevent higher temperatures

in the deoiling step itself.

The basic products of the above processes are shown in Figure 4 and Figure 5.

Figure 4: Photographs of feedstock and products: Dewaxing: feedstock (raffinate, left), base oil product

(middle), and slack wax (right)



19

Figure 5: Photographs of feedstock and products: Combined Dewaxing and Deoiling: feedstock

(raffinate, far left), base oil product (second left), hard paraffin wax (second right), foots oil (far right)

3.2 Industrial AADC systems

3.2.1 Properties and general parameters

Cooling systems cooling air, liquids and solids, are widespread for private and industrial applications.

Industrial cooling systems are essential to many types of manufacturing processes. This can include

the removal of excess heat from a process or, as in this specific case, the separation fractions with

different melting/freezing points from one another.

Ammonia absorption refrigeration is widely used in industrial sectors where the total demand of

cooling can be extraordinarily high. Ammonia is an excellent refrigerant for cooling systems which

are either driven by steam, pressurized hot water or directly with the exhaust gases. Main aspects of

AADC systems are:

- Able to reach very low temperatures

- Driven by heat, which results in very low operational costs if the heat is residual heat

- Well partial load performance, whereas efficiency increases at partial load

- High durability of the system due to very few moving components

- Specific safety measures required due to ammonia as refrigerant (depending on the application

area)

- Relatively high investment costs

- Relatively low maintenance costs

AADC systems are able to produce cold down to -60 °C using (excess) heat as the main energy source.

The liquid ammonia evaporates at low (sub-atmospheric) pressure while cooling down the reactor

feed (monomers) in the evaporator. The ammonia absorption refrigeration process/cycle can be

subdivided into the following four basic steps, as to see in Figure 6.



20

Figure 6: Simplified functional scheme of an AADC system

Step 1:

In the evaporator (I) liquid ammonia is evaporated at low (subatmospheric) pressure by taking the

required energy ('heat of evaporation') from surrounding area. Upon which the product (in H&R’s

case raffinate), which is pumped through the evaporator in a separate circuit, is cooled down ('chilled

medium').

Step 2:

The ammonia vapour generated in Step 1 is transferred to the absorber (II), where it is taken up

(absorbed) by an aqueous ammonia solution with a low ammonia content ('poor solution') leading to

an ammonia enriched solution ('rich solution'), which is fed to a rectification column that is

connected to the desorber (III).

Step 3:

By heating up in the desorber (III) the 'rich solution' generated in Step 2 is separated into 'poor

solution', consisting mainly of water and 'vapour', consisting mainly of ammonia.

The 'poor solution' is sent back to the absorber to again absorbing ("used") ammonia vapour and

producing a 'rich solution'. Whereas the 'vapour' is purified in the rectification column to result in



21

nearly pure ammonia vapour. The vapour stream leaving the rectification column consists of nearly

pure ammonia and is subsequently liquefied in the condenser.

Step 4:

The ammonia vapour generated in Step 3 is liquefied in the condenser (IV) and again fed into the

evaporator.

3.2.2 H&R’s AADC systems in Hamburg and Salzbergen (Germany)

H&R operates two AADC systems. One in the refinery in Hamburg and one in Salzbergen. The

AADC systems produce the cold required for the dewaxing and deoiling process in the production of

base oil and waxes. The feed raffinate has to be cooled down to about -20 °C. For this purpose, the

ammonia needs to be cooled down to about -30 °C.

The cooling capacity is xxxx (-32 °C) for the AADC in Hamburg and xxxxxxxx (-30 °C) for the

AADC in Salzbergen. Both systems are driven with steam of about 11 bar(a), which is generated on-

site with heat from the waste incineration. The content of 'cooling medium' within the system is

approx. xxx for the AADC in Hamburg and approx. xxxx for the AADC in Salzbergen. The two

AADC systems operated by H&R have an expected remaining life time of at least 20 additional years

(Hamburg approx. 35 years, Salzbergen approx. 20 years) assuming current operating conditions and

normal maintenance.

The process parameters for the two AADC systems partly differ from each other. The subsequent

description focuses on the system in Hamburg. In addition the parameters of the system in Salzbergen

are provided in brackets next to the Hamburg values.

Desorber and rectification:

In the desorber, which is supplied with overheated steam of up to 230 °C (Salzbergen 340 °C), boils

a fluid mixture of about 12 % ammonia and 88 % water. Inside the desorber there is a temperature of

165 °C and a pressure of 15 bar(a). The emerging steam phase contains a high content of ammonia

and forms a thermodynamic equilibrium with the liquid phase. The steam is purified of residual water

in the rectification column. The head product of the rectification column finally is almost water-free

high-pressure ammonia steam with a temperature of 50 °C. Parts of the condensate are led back to

the column, for the purpose of better clearing of the ammonia containing steam from the residual

water.

Condensation process:

The ammonia steam is condensed in a water-cooled condenser and collected in a collector.

Afterwards, the condensate is cooled down to 0 °C (Salzbergen +5 °C) in a cold exchanger in order

to improve the cooling capacity in the following expansion.

Evaporation process



22

In the expansion valve the subcooled condensate is expanded to evaporating pressure of about 1 bar(a)

and as a fluid-steam-mixture with a temperature of -32 °C (Salzbergen -30 °C) proceeds further to

the evaporator. From the evaporator the liquid ammonia is transported to the different consumers,

where a part of the ammonia is evaporated and thus the required cold is generated. The evaporated

ammonia as well as the residual fluid are pumped back to the evaporator. The steam is led to the cold

exchanger and the liquid ammonia is pumped back to the consumers.

Superheating of the steam

The saturated ammonia steam which is led to the cold exchanger is superheated by the bypassing

condensate to a temperature of up to +25 °C (Salzbergen +30 °C) and lead to subcooling of the

condensate.

Bleed

The condensate that flows to the evaporator contains residual water. This water cannot evaporate in

the evaporator. To prevent accumulation of water in the evaporator, the water (the so called “bleed”)

needs to be removed from the ammonia evaporation cycle to maintain the right ammonia

concentration.

Subcooling of the poor solution

From the desorber the poor solution (11-12 % ammonia, approx. 164 °C (Salzbergen 165 °C)) is led

to a solution-heat exchanger. Where it is subcooled to about 40 °C. In the expansion valve the poor

solution is relaxed to evaporation-pressure (approx. 1 bar(a)) and then led to the absorber.

Absorption process

The NH3-steam generated in the evaporator and the cold exchanger are, just as the poor solution, led

to the absorber. The two currents mix and form the rich solution (approx. 26 % ammonia). The heat

of solution generated in this process is transferred to the cooling water. The rich solution, which has

now a temperature of about 35 °C (Salzbergen 34 °C) is collected.

Heating of the rich solution

The rich solution is transferred to the solution heat exchanger and heated to about 135 °C. It is then

used as feed for the rectification column. A part of the cold poor solution is also led to the rectification

column to improve the heat ratio of the plant.

Finally, the cycle is complete. The process is very complex and highly demanding to the hardware

components due to the extreme temperatures, pressure levels and ammonia concentrations. The

constructions, piping and equipment are made of (cold resistant) carbon steel, which known as a

material that can be used under these conditions. Exemplarily, Figure 7 shows the AADC system in

Salzbergen (see also CSR).



23

Figure 7: H&R’s AADC system in Salzbergen (Germany).



24

3.3 Corrosion and corrosion inhibition in AADC systems

3.3.1 General remarks on corrosion

Corrosion is the gradual destruction of materials by an electrochemical reaction. The most important

form of corrosion occurs when steel is exposed to an aqueous environment causing the metal to rust.

For the construction of absorption cooling systems using ammonia water mixture as working fluid

('cooling medium') most often carbon steel is used due to its availability, economic advantages and

the easy handling, including forming or welding. The corrosion of carbon steel is an electrochemical

process involving a chemical change of iron to iron oxide and an electrical process involving electron

current flow. In an anaerobic system under the given parameters of an AADC system it is considered

that the following reactions are most common:

(1) Fe + H2O FeO + H2

(2) 2 FeO + H2O Fe2O3 + H2

(3) 3 FeO + H2O Fe3O4 + H2

These processes cause a decomposition of the material. The decomposition of the material influences

the integrity of the whole cooling plant. Additionally, the formation of gaseous hydrogen occurs,

which is a key problem for ammonia based cooling systems. The non-condensable hydrogen

accumulates in the system, primarily in the condenser and absorber units. As a consequence, hydrogen

absorbed in those units drastically hampers the condensation and absorption process of ammonia

refrigerant.

In recirculating water systems, such as cooling or heating systems, the main factors influencing the

corrosion rate are temperature, oxygen concentration, dissolved salts, pH and solution velocity (flow

rate). When the water temperature is increased, the corrosion rate increases. Dissolved oxygen

entering the system in the water may cause severe corrosion. H&R’s Ammonia absorption cooling

systems are operated at temperatures between 35 °C and to 165 °C. Each AADC system is designed

as a closed system. Generally, compared to an open system the potential for oxygen corrosion issues

is reduced, as the recirculating solution is usually not in contact with air (oxygen).

The flow rate is another crucial factor when evaluating the corrosion rate of recirculating water

systems. It has a direct influence on the erosion-corrosion, also known as Flow Accelerated Corrosion

(FAC). This effect can be defined as the acceleration in the rate of corrosion attack on metal,

proportional to the relative motion of a fluid at a metal surface. It typically occurs in structures where

flow direction or velocity is altered (e.g. pipe bends (elbows) or tube constrictions). It is mostly

prevalent in systems using aluminium or copper alloys, as well as carbon steel. Erosion-corrosion can

be characterized as a mechanical removal of the protective oxide layer from a metal surface by a

continuous flow of fluid. Once the metal surface is exposed, increased corrosion rates can be

observed. If the protective metal oxide layer cannot be formed/regenerated quickly enough,

significant damage to the system may occur. Again, it is important to consider the temperature and

pH of the circulating solution. Higher temperatures and, lower local flow rates minimize the risk for

erosion-corrosion.



25

A major problem of corrosion phenomena in AADC systems is that usually there are many variables

like ammonia concentration, temperature level, existing impurities, possible pre-treatment of the

surface, etc. which can greatly influence the corrosion rate. This is important because even low

corrosion rates have to be avoided because of the accompanied formation of non-condensable gases,

which influence the thermodynamic cooling process negatively. Possible gas forming reactions are:

(4) Fe + 2 H2O Fe(OH)2 + H2

(5) 3 Fe(OH)2 Fe3O4 + 2 H2O + H2 ('Schikorr reaction')

(6) 2 NH3 N2 + 3 H2

3.3.2 Consequences of the absence of corrosion inhibitors

AADC systems operated without corrosion inhibitors or with incorrectly adjusted corrosion inhibitor

systems can show serious corrosion induced damage from oxygen pitting, galvanic action, and crevice

attack. The absence of a suitable corrosion inhibitor or the use of an unsuitable corrosion inhibitor for

the respective AADC system could lead to equipment failure within a few months. Consequently, the

plant would have to be shut down for repairs for a time of at least several weeks. The H&R base oil

and wax production is intended to operate 24 h/day at 7 days/week without interruption (despite of

regular maintenance periods as described in the CSR).

A discontinuation of the use of sodium dichromate will lead to unsafe operating conditions because

heavy pitting will occur. Consequently, the cooling system is not functional and can no longer be

operated. Both refineries are joint productions, where the production processes are interdependent in

order to make use of all side products (just as the waxes and base oil) and energy streams (excess

heat/cold, waste water) that are generated. In fact, the process step of de-waxing/de-oiling is a key

process in the refineries and essential for most products generated there and therefore unavailability

of the required cooling capacity will lead to a complete standstill of the refineries because the key

products cannot be generated without cold.

A longer production stop would entail high losses in capacity with immense economic impacts, as

described in the next chapters and in the SEA. These problems are accompanied severe occupational

threats as a result of leaking tubes and pipes which are operating under immense pressure and high

temperature. Although replacement costs for material and labour are one important cost factor, the

reduced plant efficiency would create costs as a result of a lowered output and a reduced product

quality.

3.3.3 Corrosion inhibition with sodium dichromate

Corrosion resistance in the context of this application refers to the ability of carbon steel incorporated

in the AADC system to withstand gradual destruction by electrochemical reaction with its

environment. For the given application, inhibiting electrochemical destruction is the crucial for

assuring the longest possible life cycle of the AADC system and all its implicit parts. Corrosion

inhibitors can be categorized according to basic quality criteria which are inhibitive efficiency,

versatility, and toxicity. Furthermore, chemical and thermal product stability as well as quality of the

corrosion inhibitor have to be guaranteed. The use of sodium dichromate has proven to be essential

in the AADC system due to its excellent corrosion resistance and in situ repair properties regarding



26

the conditions (e.g. basic medium, temperature, and flow rates) under which the system is operated.

Strong oxidizing corrosion inhibitors such as sodium dichromate form a protective layer on the metal

surface containing mainly trivalent chromium, oxidized iron and oxygen, as described by the

following equations:

(7) Na2Cr2O7 + 2 NaOH 2 Na2CrO4 + H2O

(8) 9 Fe + 8 Na2CrO4 + 8 H2O 3 Fe3O4 + 4 Cr2O3 + 16 NaOH

Under the given conditions predominating in the AADC units, the use of sodium dichromate is critical

for the formation of a stable and dense protective layer. Only at temperatures > 230 °C, the formed

protective magnetite film is strong enough ('Schikorr reaction') to prevent corrosion without addition

of a corrosion inhibitor as then the erosion-corrosion rate is low enough.

In summary, the main characteristics of sodium dichromate as corrosion inhibitor in the given cooling

unit are to build up a dense protective layer at temperatures between 35-165 °C. The protective layer

needs to be formed in the absence or at minimal concentration of oxygen, as non-condensable gases

in the working fluid ('cooling medium') reduce the cooling capacity drastically. The (erosion)

corrosion rate is dependent on (local) liquid velocities; i.e. the higher the velocity, the higher the

corrosion rate. Furthermore, the facility has at the 'poor solution' (11-12 % ammonia) a pH of 9.0 -

10.0 which cannot be changed. For the 'rich solution' (about 26 % ammonia) pH is around 12. An

overview of the most important process parameters and the requirements a corrosion inhibitor in

AADC systems has to fulfil is given in Table 6.

Table 6: Important parameters and functionalities of sodium dichromate as corrosion inhibitor

Criteria Definition / Justification Functionality

Verification

method /

minimum

requirement

(Active)

Corrosion

resistance

Corrosion resistance

describes the ability of the

steel parts used in the

AADC system to withstand

gradual destruction by

electrochemical reaction

with its environment.

The main functionality of

sodium dichromate within

the system. A passivating

magnetite layer is formed

which acts as a barrier and

prevents corrosive

processes.

Corrosion

resistance has to

be ensured over

the whole

lifetime of the

AADC systems.

Non-

condensable

gases formation

The formation of non-

condensable gases has to be

avoided by the corrosion

inhibitor.

Gases would negatively.

impact the cooling

efficiency

Sodium dichromate reduces

the formation of gases like

hydrogen (H2) which are

generated during the

electrochemical corrosion

reaction of iron. (see

reactions (1) – (6))

Cooling capacity

stable over long

term.



27


Verification

method /

minimum

requirement

Temperature

The temperature in the

AADC systems ranges from

35 °C to 165 °C.

Only above 230 °C the

protective magnetite film is

formed strong enough for

corrosion prevention

without addition of

corrosion inhibitors like

sodium dichromate as the

erosion-corrosion rate is low

enough; below 180 °C the

use of a corrosion inhibitor

is critical for the formation

of a stable, dense protective

layer.

Sodium dichromate retains

its functionality within the

given temperature range.

Functional at

35 °C to 165 °C

pH

The actual pH of the 'poor

solution' (11-12 %-wt

ammonia) is 9 - 10. For the

'rich solution' (about 26 %-

wt ammonia) the pH is

around 12.

Sodium dichromate retains

its functionality within the

given broad alkaline pH

range.

Functional at

alkaline pH

Liquid velocity

The (erosion) corrosion rate

is dependent on (local)

liquid velocities. The

velocity varies within the

cooling system.

Sodium dichromate is able

to form the protective layer

at high local liquid

velocities.

Functional at

broad range of

liquid velocity

Oxygen content

An AADC system is

designed as a closed system.

Therefore, the oxygen

content of the working fluid

('cooling medium') is

considered to be very low.

Oxygen in the AADC

system would have a

negative impact the cooling

efficiency. Sodium

dichromate is able to form

the protective layer in the

absence of oxygen.

Functional in the

absence of

oxygen



28


Verification

method /

minimum

requirement

Fouling

Fouling within the AADC

system has to be minimized.

Fouling reduces the cooling

efficacy and causes other

problems such as

contamination and cleaning

procedures.

If the corrosion inhibitor

also inhibits fouling

processes no additional

inhibitor has to be added.

Sodium dichromate shows

effects against

microorganisms and has the

potential to reduce fouling.

Not quantified

Long-term

stability of the

corrosion

inhibitor

The corrosion inhibitor must

be stable and active over a

long time as it is present

within the AADC system

for decades.

Should not interfere with the

water and the ammonia in

the AADC system or the

AADC system at all,

besides forming the

passivation layer. No

undesired long-term effects

on the AADC system should

occur.

Sodium dichromate has a

proven track record of many

decades to be an effective

and safe corrosion inhibitor.

Use in AADC

H&R’s systems

for a time period

of at least 20

additional years

Adsorption/

desorption

process

Influencing the

absorption/desorption

process would influence the

efficiency of the cooling

process.

Sodium dichromate does not

affect the absorption

desorption process in an

inadequate manner.

Performance

tests; long-term

experience



29


Verification

method /

minimum

requirement

Proven

technology – for

application at

high

temperature in

desorber, very

low oxygen

content, water

rich material,

high velocity

The corrosion inhibitor must

show demonstrable

suitability for AADC

systems. Otherwise severe

security risks could occur.

This includes the leakage of

ammonia, which is not

acceptable in terms of

occupational and

environmental protection.

Furthermore, plant

shutdowns would have

severe economic impacts

(see SEA).

To date, sodium dichromate

has been used for decades in

the plant – no corrosion

issues have been observed.

Redox potential

half-cell

Information on the annual tonnage of sodium dichromate used as corrosion inhibitor in AADC

systems operated by H&R in Hamburg and Salzbergen (Germany) is provided in Chapter 4. Chapter 5

gives an overview of efforts in R&D concerning the identification and implementation of possible

alternatives to sodium dichromate as well as related approval processes. Section 5.3 provides a list of

identified possible alternatives.

4. ANNUAL TONNAGE

Sodium dichromate is used in both AADC systems operated by H&R in Hamburg and Salzbergen

(Germany). The annual tonnage is xxxx (≤ 0.01 tonnes) sodium dichromate [xxxxxxx as Cr(VI)].

During the past 17 years (2000–2017), xxx tonnes sodium dichromate, which is equivalent to xxxx

tonnes hexavalent chromium [Cr(VI)], were purchased by H&R and consumed in the specific use

applied for. The whole amount mentioned above was purchased at one occasion in 2017 and used to

refill the AADC system in Salzbergen. In the former years (2000 -2016) no concentration adjustments

took place. For more details please refer to the CSR.



30

5. IDENTIFICATION AND IMPLEMENTATION OF POSSIBLE ALTERNATIVES

5.1 Description of efforts made to identify possible alternatives

Several efforts were made during the last years to identify possible alternative corrosion inhibitors

for AADC systems. In course of these efforts, scientific literature was evaluated extensively and

experts from other companies dealing with similar cooling systems were approached. Moreover,

several other international research institutes were contacted for the Arlanxeo AfA to discuss and

evaluate the state of the art for corrosion inhibition in this type of cooling systems. Besides that, H&R

had consultations with the manufacturer of the AADC systems.

This AoA includes expert opinions from downstream users, manufactures, academic and scientific

institutions and societies to set up a comprehensive documentation on corrosion inhibition in AADC

systems and associated cooling systems.

5.1.1 Research and development activities

The field of corrosion and corrosion inhibition was extensively investigated during the last decades

by industry and scientific institutions and is due to its economic impact still of particular interest.

Corrosion inhibition techniques were investigated for the purpose of this AoA based on extensive

investigation in course of the Arlanxeo AfA, for which the applicants hold a Letter of Access (LoA).

In this context, relevant literature and databases were screened, and experts, the AADC system

manufacturer and other industrial users, were contacted. Furthermore, a third-party consultancy and

a national research institute were consulted.

For the present document this information was combined with the insights H&R gained through their

own activities. The alternatives assessed for the Arlanxeo AoA were evaluated for H&R’s specific

case, as the key functionalities differ slightly in the quantitative dimension. Both, the Arlanxeo and

the H&R AADC systems are from the same manufacturer and, besides deviations in design, function

in the same way, which is why the insights from the Arlanxeo AoA can be regarded as adequate base

for H&R. And of course, the purpose of sodium dichromate is exactly the same.

The information on alternatives form the Arlanxeo AoA was assessed on being up-to-date in a

literature desktop study conducted by H&R. Several databases were searched for new publications.

The search revealed that between 2015 and today ground-breaking achievements were not made in

context with corrosion protection in AADC systems. The alternative assessment below therefore still

represents the latest stage of knowledge and development.

Other highly relevant sources of information are the publicly available AfAs of companies which

have applied for the use of sodium dichromate in AADC systems earlier, such as the AfAs submitted

by Jacobs Douwe Egberts DE GmbH (2016), TOTAL Raffinerie Mitteldeutschland GmbH (2016),

Dometic GmbH (2015) and Borealis Plastomers B.V. (2016).

5.1.2 Consultations and directed communications

H&R consulted the manufacturer of the AADC systems in Hamburg and Salzbergen to find out

whether an alternative to sodium dichromate was available. The manufacturer has the required



31

competence to provide reliable information regarding this question. While H&R operates the AADC

systems, it is the manufacturer that conceptualises them and also provides the operating instructions,

including how to maintain the system to achieve a maximum lifetime of the system under safe

operation conditions. Part of this is also the use of sodium dichromate as corrosion inhibitor. The

technical and economic feasibility of alternatives that were initially discussed in context with the

Arlanxeo AfA, were discussed with the manufacturer of H&R’s systems. The knowledge gained in

this consultation are included in the alternative assessment in Chapter 6 below.

Furthermore, information on the status of alternatives was collected in consultations earlier by

Arlanxeo in course of their AfA, to which H&R holds a LoA. The extensive information derived in

this context must not be disregarded in order to assess alternatives for H&R in a comprehensive way.

Therefore these consultations and directed communications are recapitulated in the following:

In 2003 consultation of various chemical companies, water technology companies and the Materials

Technology Institute (MTI) for information of potential alternatives to sodium dichromate in AADC

systems were conducted. Furthermore a company was identified that had used molybdate as an

alternative but had switched back to sodium dichromate due to massive corrosion problems. In 2009

the above mentioned survey was repeated by Arlanxeo’s corrosion specialists and additionally two

suppliers of ammonia vapour absorption installations were contacted. In 2015 a water

technology/treatment company was invited to assess alternatives. Also specialized research institutes

for cooling engineering were approached. An extensive literature study had already been conducted

in 1999. This literature was assessed for this AoA and taken into consideration, where applicable. In

another third-party study, conducted in 2015, the report from 1999 was reassessed and complemented

based on updated scientific information, information requests in an international scientific forum and

most importantly discussion with downstream users and manufactures.

Finally, the company Dometic Holding AB (Dometic), a manufacturer of small scale cooling systems,

which has also filed an AfA for sodium dichromate as a corrosion inhibitor for AADC systems, was

contacted. The company has a promising proprietary alternative corrosion inhibitor for the small scale

absorption cooling units (e.g. for minibars, recreational vehicle refrigerators and medical cold

equipment) they produce under development. Long-term performance tests are being conducted by

Dometic and will, according to the AfA, continue for several years. The consultation revealed that so

far it is not known how this alternative would perform in AADC systems on much larger industrial

scale. No tests have been conducted because the substance is not available to the public. The long-

term performance of the proprietary system is apparently still under review. (Dometic GmbH, 2015).

All in all, none of the consultations led to the identification of a feasible alternative for sodium

dichromate for Arlanxeo’s AADC systems (further details are provided in the Arlanxeo AfA

(Arlanxeo Netherlands B.V., 2015)).

Against the background of these R&D efforts, no alternative corrosion inhibitor has proven technical

or economic suitability in ammonia water based cooling systems by today. To provide a substantiated

argumentation, a detailed discussion of several possible alternatives that were also included in the

Arlanxeo AfA is described in Section 6.3 specifically in relation to H&R’s AADC systems. Most



32

important, only very limited experience exists with regard to the real-life use of alternative corrosion

inhibiting substances in AADC systems.

5.2 Overview on the process of alternative development and industrial implementation

For many decades, AADC systems made of carbon steel have constituted a safe and reliable cooling

technology for miscellaneous industry sectors. Safety and reliability was ensured by using sodium

dichromate as corrosion inhibitor enabling high performance under specific process conditions.

Indeed, scientific and technical research was performed over the last years suggesting a variety of

replacement corrosion inhibitors in literature. Different patents are available, describing corrosion

inhibitor alternatives for AADC systems.

Nevertheless, most alternatives discussed in scientific and technical literature have in common that

they were not tested under realistic conditions in large-scaled systems and for a realistic time span.

Scientific results on corrosion inhibition are often gained from tests with metal stripes, exposed to

chemicals in autoclaves for a short time or in lab-scale cooling devices. Such results are not

necessarily comparable to cooling units with several thousand kW cooling power. This is also stated

by a company in this sector which gained extensive experience during years of testing on test vessels

and on actual machines incorporating an absorption refrigeration cycle. It was concluded that there is

no simple relationship between tests carried out in simulation vessels and those under real machine

conditions. Generally, good behaviour of a corrosion inhibitor in simulation vessels does not imply

that it will automatically operate well on a real machine. Tests on simulation vessels can therefore

only be used as preliminaries to select families of products to be tested (Guerra 2003).

For the development and industrial upscaling of a possible alternative for sodium dichromate as

corrosion inhibitor for ammonia absorption systems made of carbon steel, several phases bringing an

alternative step by step to final application would be necessary to ensure a safe use over of the

expected life time of the cooling plant (up to 50 years).

Phase I: Identification of alternatives and implementation on a laboratory-scale

As a first step, alternatives to dichromate-based systems have to be identified and evaluated. Detailed

description of possible alternative substances is provided in Section 6.3 of this AoA. The efforts show

that the information available is of heterogeneous quality. This initial development phase is dedicated

to screen those alternatives potentially applicable within the pool of available substances and

techniques. Sources for such a screening are: literature studies, patent examinations, the evaluation

of existing solutions in other areas, competitor analysis, and of course the information gathered in

course of the preparation of this AoA must also be taken into account.

As a second step of phase I, potential alternatives have to be tested extensively at the laboratory level.

It has to be assured whether the different components of the alternative corrosion inhibitor system

work together properly or not. Throughput time for producing and testing a sample is in the order of

weeks; there is no specific overall throughput time for the screening phase as it varies largely with

the number of alternatives tested. Multiple iterations are often needed before a promising set of

alternatives is defined after having passed the test requirements at this stage. For initial laboratory



33

testing, simple test vessels can be used in this phase. This allows no detailed but a rough comparison

of the tested alternative systems. The testing of samples is done according to several standardized

methods. First, the quantity of the active corrosion inhibitor has to be measured, then performance

needs to be checked by some relevant analytical methods. The current corrosion inhibitor (sodium

dichromate) should be incorporated in the testing as a reference in order to compare samples that are

produced in different laboratories or at different times.

Phase I may require iterative processes to refine identified alternatives and time needed heavily

depends on testing capabilities. The process is completed with the setup of a pilot system to be further

evaluated in the up-scaling phase. According to an expert opinion from a research institute for cooling

engineering, many potential alternatives are described in literature, but there is still no satisfying drop-

in alternative available for industrial use in ammonia based cooling systems. It is highly

recommended to start a project on European Union (EU) level with experts from industry, academics

and associations to investigate the implementation of alternative corrosion inhibitors in different types

of cooling systems. For setting up such a project, a lead time of one year is necessary to define scope,

members and milestones and to draft the project structure. The according identification and validation

step of potential alternatives takes at least 3 - 6 years and entails costs between EUR 300 000 to EUR

500 000.

Phase II: Up-scaling and test in relevant environments

After identifying and testing potential alternatives on the laboratory scale, reproducibility of those

corrosion inhibitor systems has to be proven on the application level of the specific use. Therefore,

the pilot system has to be up-scaled and validated in the relevant environment (e.g. varying cooling

temperatures or performance). Monitoring of robustness and stability of the process using the

alternate corrosion inhibitor must be carried out closely. As an example, this step had been performed

for more than 8 years by Dometic for their, compared to H&R’s systems, small scale applications

(Dometic GmbH, 2015).

Furthermore, the validation of the up-scaled pilot systems includes checks for approvals by authorities

concerning plant and process safety. Phase two will take additional 7 years if no major drawbacks

occur and will generate costs in the same range as Phase I between EUR 300 000 to EUR 500 000.

The challenge in this step is, that unintentional, uncontrolled release of ammonia needs to be avoided

by all means, which is why close long-time monitoring is essential, at least for 1 to 5 years for small

scale applications (Dometic GmbH, 2015). Altogether, 7 years the minimum time needed for the

completion of Phase II.

Phase III: Implementation on existing facility

In the last phase, the outcome of Phase I and II has to be implemented or adapted into the existing

AADC systems operated by H&R. Systems may have to be partly reconstructed and modified to

facilitate drop-in alternatives. In H&Rs case, the timeframe for such modifications with the lowest

impact on production, is the time of the regular maintenance window of the AADC system, which is

conducted every five years.



34

After the implementation, monitoring of robustness and stability of the process by using the alternate

corrosion inhibitor under the industrial circumstances is considered necessary, as long time

experience must be gained with any alternative to ensure a safe and reliable operation and functioning

of the system and the absence of corrosion and pitting. The monitoring needs to be conducted over a

long time period, ideally at least until the next maintenance of the subsequent production line takes

place after 5 years.

In this context it is of utmost importance to have the possibility to keep the system running in case

the (technical or chemical) alternative fails. For this purpose, the sodium dichromate must be

available as corrosion inhibitor until the reliability of an alternative has been proven.

An illustration of the development process including the above described phases I-III can be found in

Figure 8.

Figure 8: Expected timeframe of sodium dichromate substitution in the AADC systems in Hamburg and Salzbergen (Germany)

As clearly outlined, passing Phase I and II will take up to 15 years. Assuming that initiatives will start

in 2017, it is anticipated that the process can easily take until 2032. The next maintenance window

for the connected production plant, which is accompanied by a temporary production stop, will also

take place in 2032 (five year rhythm with the latest window in 2017). At least another five years are

required for performance monitoring, adding up the overall required time to 20 years. Besides this, it

has to be taken into account that the remaining life time of the AADC systems operated by H&R is

at least 35 years (Hamburg) and at least 20 years (Salzbergen)1. Therefore, end of operation of these

AADC systems is estimated for the years 2037 to 2052 respectively.

The challenging issue in this context is evident in the fact that H&R is the operator but not the

manufacturer of the AADC systems, and downstream user of sodium dichromate as corrosion

1 The AADC systems were installed at different times. The system in Salzbergen was installed in 2000 while the one in

Hamburg was installed in 2012. AADC systems can have an overall lifetime of more than 50 years.



35

inhibitor. While H&R indeed operates the existing systems safely, their core business is not the

conception and design of AADC systems. This competence lies at manufacturers of such systems,

which H&R relies on in this context. The ability to research and develop an alternative corrosion

inhibitor “from scratch” in the necessary dimension is on the other hand more a topic for scientific

research. Nevertheless, it is clear that a solution needs to be found. H&R is aware of their

responsibility as operator of AADC systems to contribute to the quest with all the possibilities they

can offer. This includes the willingness to become involved in research wherever their competences

and facilities can be of help, continuation of desktop research to stay on track with developments and

close follow-up on activities of other operators and suppliers of AADC systems as well as ongoing

research. In any case it is in the interest of H&R to contribute to increase the knowledge about the

reliability of promising alternatives in the long term use. Especially after the assessment of promising

alternatives on small scale in Phase II, H&R could contribute in the testing in large scale facilities

under realistic conditions and in Phase III, when it comes to the actual implementation of an

alternative into real-life systems and the required monitoring throughout the following years.

5.3 List of possible alternatives

As a result of the efforts described in Chapter 5, the most promising alternative corrosion inhibitors

are discussed in the following chapter. Beside the one-to-one replacement of the corrosion inhibitor,

the impacts of a complete technology change, such as the implementation of a Vapour Compression

Cooling (VCC) system will be elucidated in the following Section 6.1. Additionally, it will be

discussed if a replacement of specific corrosion prone parts of an AADC systems is suitable to

ensure a safe and reliable performance of the system (see Section 6.2). The evaluation of alternative

corrosion inhibitors is described in Section 6.3.

The potential alternative substances are classified according to their relevance as Category 1 or

Category 2 alternative. An overview is provided in Table 7. In case of Category 1 alternatives, initial

R&D efforts on ammonia/water based systems can be found. Although partly tested on test vessels

or commercially available small scale units, they are far away from being applied on the industrial

scale. Respective R&D is mostly of basic nature than ongoing. Category 1 alternatives are discussed

in detail in the following Section 6.3.2.

As for Category 2 alternatives, only indications for the use as corrosion inhibitor for carbon steel was

found in the course of the literature review. Results are restricted to the laboratory scale and no

indication for the use in AADC systems is present. In addition, Category 2 alternatives exhibit

technical limitations leading to dismissal. Category 2 alternatives are therefore only tabulated in

Appendix 1.

Table 7: Categorized list of alternative corrosion inhibitors

Chapter Cr(VI) free corrosion inhibitors

Category 1

6.3.2.1 Molybdate

6.3.2.2 Sodium nitrite



36

Chapter Cr(VI) free corrosion inhibitors

6.3.2.3 Silicates and water glass

6.3.2.4 Zinc containing corrosion inhibitors

6.3.2.5 Strong alkaline solutions

6.3.2.6 Phosphates and phosphonate compounds

6.3.2.7 Rare Earth Metal Salts (REMSs)

Category 2

Appendix 1

Tartrate compounds

Benzoate

Glutamate

Succinic acid

Organic inhibitors

Azole and azolines

6. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES FOR THE

AADC SYSTEMS OF H&R

As mentioned above, H&R operates two AADC systems applying sodium dichromate as corrosion

inhibitor in their refineries in Hamburg and Salzbergen (Germany).

For the three AACD systems, 3 different alternatives are discussed:

- Section 6.1: Replacement (change) of the cooling system

- Section 6.2: Replacement of corrosion prone parts

- Section 6.3: Substitution of sodium dichromate as corrosion inhibitor

6.1 Alternative 1: Replacement (change) of the cooling system

6.1.1 Properties/Description

VCC, a technique where the refrigerant undergoes phase changes, is widely used for cooling and air

conditioning, e.g. in automobiles, buildings, refrigerators, oil refineries and chemical processing

plants. Generally, in such a cooling system the enthalpy of vaporization occurring at the liquid

gaseous transition is used for cooling effects. In most cases, VCC units do not depend on the use of

a corrosion inhibitor system.

6.1.2 Technical feasibility

VCC systems have cooling capacities of a few Watts (W) to several MW. Accordingly, a VCC

system is potentially able to provide enough cooling load for H&R’s plants in Hamburg and



37

Salzbergen (Germany) which require xxxxxxxx. Temperatures down to about -30 °C are required.

VCC systems can provide the required cold and reach temperatures down to -40°C.

Differences between the two technologies, AADC and VCC systems, are listed in Table 8.

Table 8: Advantages of the two cooling technologies

VCC systems AADC systems

Better dynamics

Low heat release / heat dissipation

Heat as energy source is available at the

applicants’ sites from other processes

Extraordinary good partial load behaviour

Low consumption of electrical energy

Robust, reliable and long-lasting technique

Low maintenance effort required

When the old compression systems were to be replaced, cost-efficiency, which is in this aspect closely

connected to resource efficiency, was a main argument to implement AADC systems in 2000

(Salzbergen) and 2012 (Hamburg).

Furthermore, to switch to a VCC system the whole cooling system with all its components, vessels,

pipelines, control units must be exchanged. The AADC systems run by H&R are of enormous size

and complexity. Also the complexity of a VCC system is high, posing serious challenges for the de-

construction of the old and building of the new system.

On the other hand, H&R has experience with VCC systems, since they are used for other purposes

on the sites in Hamburg and Salzbergen, and before the AADC systems were implemented, VCC

systems were used in the production of base oil and waxes. So, all in all VCC systems are considered

to be technically feasible.

6.1.3 Economic feasibility

The economic impacts of a transition from AADC towards VCC are discussed as non-use scenario

(NUS) 1 in the SEA. The findings from the SEA are summarised here. For more detail please refer

to the SEA.

For the installations at H&R’s sites, the use of a VCC installation instead of an AADC installation

would mean a complete replacement of the existing technology. The site development does not allow

to build a new cooling plant additionally to the existing one, due to space limitations. The existing

cooling plant would have to be destructed first before a new one can be constructed. Due to the fact

the site is located in the vicinity to a residential area, costs for housing and a building for noise

protection must also be included.



38

H&R expects that the current cooling systems (using ammonia absorption technology), could last for

at least 20 years more with very few routine maintenance efforts. For this reason, the purchase of a

new cooling system would bring forward an investment that otherwise would only happen in 20 years.

The new cooling system is expected to last for 20 years after and therefore, the calculation of the

annual cost of this investment was done considering this period as the total lifetime, 20 years of earlier

investment and xxxxxxxxxxxxx as the total amount required to purchase the new equipment. Since

the lifetime of the new equipment is assumed to be exactly the same as the remaining life of the old

equipment, the net present value (NPV) was calculated considering 20 annual payments, therefore

resulting in an NPV that amounts exactly to the total amount of the investment: xxxxxxxxxxxxxxx.

Another factor that adds to the economic impacts in case of non-authorisation is the production

downtime caused by the implementation of the new cooling system. H&R expects that the

implementation process of the new technology would take approximately 2 years. Meanwhile the

new cooling system is implemented, production lines will have to be shut down resulting in

opportunity cost for the company. The total duration while the production would have to be stopped

is estimated to take xx days. The plants are running at full capacity and continuously (24 hours/day,

7 days/week), not being able to replace the cooling system without a production stop. The calculation

of the opportunity cost during this period was done using the added value foregone. The calculations

in the SEA reveal that a total of xxxxxxxxxxxx in value added foregone need to be added to the

economic impacts in H&R’s case.

Additionally, H&R has analysed its future cooling costs in the case the new cooling system would be

installed. Considering the whole period of assessment (20 years), the NPV of the additional annual

costs for this period is an indicator of the economic benefit of switching to the alternative. The NPV

of these yearly additional costs over a period of 20 years sums up to xxxxxxxxx.

Summing up all economic impacts that would arise from the switch to VCC (new investment, loss of

capacity, downtime) and deducting the amount that would be saved due to reduction in the production

costs, the net economic impacts of the NUS can be summarised as follows in Table 9.

Table 9: Net Economic Impacts – replacement (change) of the cooling system

Type of impact [EUR]

Investment in a new cooling system xxxxxxxxx

Value added foregone due to downtime xxxxxxxxx

Additional operational costs with VCC xxxxxxxxx

Net economic impacts 40 400 313

6.1.4 Reduction of overall risk due to transition to the alternative

The overall risk associated with a complete replacement of the cooling technology depends on the

particular technology used. Since, to the current state of knowledge, the information collected by

H&R on this topic and not at least due to practical experience at H&R with big VCC systems in their



39

refineries, no corrosion inhibitor, and thus no sodium dichromate, is required for VCC systems.

Therefore the use of a VCC system would eliminate the risk from the use of sodium dichromate.

6.1.5 Availability

The general availability of VCC systems is not regarded as critical, because different companies do

offer the manufacturing of such systems. However, regardless of the fact that an exchange in the next

years is not advisable from an economic point of view, the practical installation of VCC systems

poses serious challenges. The whole cooling system with all its components like vessels, pipelines,

control units etc. would need to be exchanged completely. The AADC systems of H&R are highly

complex and of enormous size. The installation of equally large and complex VCC systems poses

serious challenges, because of the restricted availability of free space on the refineries’ sites, which

is why the old system would have to be deconstructed before the new system could be built (see also

section economic feasibility).

6.1.6 Conclusion on suitability and availability

Even though technically feasible, the installation of a VCC system would be accompanied with

considerable economic impacts such as investment costs, downtime of production, decreased

production capacity. On the other hand, operational costs could be reduced with the new system.

From a technical perspective, for the current AADC systems fewer maintenance efforts are needed

and these cooling systems generally possess a longer overall lifetime (10–20 years vs. up to 50 years).

Overall, to date change to a VCC system is not considered to be an applicable alternative for H&R

for economic reasons.

6.2 Alternative 2: Replacement of corrosion prone parts

6.2.1 Properties/Description

The replacement of corrosion prone parts of the existing AADC systems with components that are

more corrosion resistant, e.g. stainless steel could be another possibility to prevent material

degradation. Here only parts of the existing cooling units in Hamburg and Salzbergen would have to

be replaced.

6.2.2 Technical feasibility

Literature research showed that stainless steel is often discussed as being corrosion resistant to

ammonia water based systems. Whether the replacement of parts made of carbon steel by stainless

steel allows operating the AADC system reliably without sodium dichromate was investigated for

this AfA.

A replacement would be needed at least for the most corrosion prone parts, which are in contact with

cooling medium at high temperature. It was discussed whether these parts should be made of stainless

steel to reduce corrosion. The remaining parts that are in contact with concentrated ammonia could

remain constructed in carbon steel. Parts that would be needed to be replaced H&R’s AADC systems

are, at least, the desorber, the solution heat exchanger and corresponding piping till as well as the



40

absorber condensers, all constructed in carbon steel and to be replaced by new equipment/piping in

stainless steel. Beyond this it has to be investigated if absorbers itself maybe do not need to be

replaced, due to lower temperature and overall milder corrosion conditions. Since the applicant’s

AADC systems are large and complex, the practical work to exchange of the parts poses a serious

challenge.

Beside stainless steel also carbon steel equipment which is permanently coated by a passivating layer

was discussed as an option. Such techniques are commercially available, but this would as well

implicate the replacement of large parts of the AADC system.

To discuss the feasibility of this approach, the manufacturer of H&R’s systems was contacted by

H&R to gain insight on the latest state of knowledge in this context. The statement received (see

confidential Appendix 3) on this issue says that:

1. Materials with better, maybe even sufficient, corrosion resistance are not widely spread within

large AADC systems.

2. However, the idea is promising from a technical standpoint, but no long term experience is

available.

This is supported by the investigations conducted by Arlanxeo for their AfA, where a German

research institute was also contacted for this purpose. The research institute concluded that stainless

steel systems of a size similar to the Arlanxeo AADC, which is of a comparable dimension to H&R’s

systems, are currently not operated and, even more important, no reliable conclusion about the

presence or absence of corrosion inhibitors in such systems can be drawn.

As already mentioned in Section 3.3, the use of carbon steel in AADC systems is preferred due to

economic advantages and better machinability. Further literature research substantiated the

statements above, revealing that results on corrosion resistance of stainless steel in ammonia water

based systems are not consistent. Several authors described corrosion problems on stainless steel and

chrome plated steel when tested in ammonia water based systems (Mansfeld and Sun, 2003; Griess

et al, 1985). These results were also heavily influenced by the process temperature. With higher

temperatures, corrosion rates increased significantly (Behrens 1998, Kreysa and Schütze 2007).

Recently, Moser et al. (2011) investigated the hydrogen production rate in two test facilities (stainless

steel and carbon steel) for ammonia water based absorption heat pumps at different temperatures as

a marker for corrosion performance. It was shown that mild carbon steel (ST37) induced lower

hydrogen production than stainless steel.

Generally, it can be concluded, that also stainless steel is subject to corrosion in ammonia water based

systems, especially at higher temperatures. As mentioned above, at present, no information exists on

corrosion inhibition for systems made of stainless steel.

6.2.3 Economic feasibility

The economic impacts of a transition from AADC towards VCC are discussed as NUS 2 in the SEA.

The findings from the SEA are summarised here. For more detail please refer to the SEA.



41

The investment costs for stainless steel parts would be xxxxxxxxxxxxxxxxxxxx for one cooling

system (equipment costs only). This does not include labour costs for deconstruction and construction

of the new system. An engineering factor of 3 needs to be added to the cost estimate for a replacement

of the entire cooling system. This engineering factor is needs to be applied to arrive at a realistic

estimate of the total cost to replace the corrosion prone parts of the system.

H&R expects that the current cooling system (using ammonia absorption), could last for 20 years

more with very few routine maintenance efforts. For this reason, the purchase of new equipment

would bring forward an investment that otherwise would only happen in 20 years. Since there is

absolutely no experience available with stainless steel parts in AADC systems in the industrial scale,

the lifetime of this equipment cannot be estimated, but is expected to be considerably shorter than the

current one. However, to keep the worst-case approach, 20 years of functional lifetime of the

stainless-steel parts are taken as input for the following calculations. In addition, it is expected that

due to the lack of experience, the costs for routine checks and maintenance will be considerably higher

than with the current system, but also these costs were not factored in here.

The new equipment is expected to last for 20 years. Therefore, the calculation of the NPV of this

investment was done considering 20 years of total lifetime, 20 years of earlier investment and xxxx

xxxxxxxxxxxxxxxx as the total amount required to purchase the new equipment, dismantle the

existing one and install the new equipment.

Since the lifetime of the new equipment is exactly the same as the remaining life of the old equipment

(conservative assumption), the NPV was calculated considering all the 20 annual payments, therefore

resulting in an NPV that amounts exactly to the total amount of the investment, xxxxxxxxxxxxx

xxxxxxxxx.

Similar to NUS 1 – change to another cooling system – the expected minimum downtime for the

replacement of parts by stainless steel parts is xx days. Therefore, the economic impact resulting from

the downtime in the NUS – replacement of parts – is the same as in the abovementioned scenario 1.

The monetised impact in this case is xxxxxxxxxxxxxxxxx.

In sum the net economic impacts for the replacement of corrosion prone parts can be summarised as

follows in Table 10.

Table 10: Net Economic Impacts – replacement of corrosion prone parts

Type of impact [EUR]

Investment in a new cooling system xxxxxxxxxxxxxxxxxxxx

Value added foregone due to downtime xxxxxxxxxxxxxxxxxxxx

Net economic impacts 16 301 935 – 22 301 935



42

6.2.4 Reduction of overall risk

For the assessment of environmental and human health related risks associated with a replacement of

corrosion prone carbon steel parts with stainless steel parts an external technical expert review was

carried out in course of the Arlanxeo AfA. Based on these information, it was stated that such a

replacement had never been performed for large ammonia water based cooling systems in the past.

As evaluated in the section on technical feasibility (6.2.2), it is not known whether a modified AADC

system, with replaced metal parts, could run in a safe and reliable manner without additional corrosion

inhibitors. Moreover, no experiences exist which parts have to be replaced. There is a substantial risk

remaining that not all necessary parts are replaced. For risk mitigation in terms of safety, the use of a

corrosion inhibitor in a modified AADC system seems essential.

In summary, no reliable experience exists on the safe long-term operation of an AADC system made

of stainless steel of the size operated by H&R in Hamburg and Salzbergen (Germany). It is not known,

whether a corrosion inhibitor has to be used within these systems. If the risks are not properly

controlled, this could lead to accidents and the uncontrolled release of up to 100 % ammonia into the

environment with severe impacts on environment and human health.

6.2.5 Availability

All necessary parts of the AADC system could be built with stainless steel, which is substantiated by

the information provided by a manufacturer of cooling units. Availability is therefore not considered

as critical.

6.2.6 Conclusion

From the current state of knowledge, the replacement of critical parts cannot be regarded as

technically feasible for H&R’s AADC systems in Hamburg and Salzbergen. There is no long-term

experience whether an ammonia water based cooling system made of stainless steel can be operated

in a safe and reliable manner with or without adding a corrosion inhibitor. It is likely that a partial

replacement of corrosion prone parts would still make the presence of a corrosion inhibitor

mandatory. Furthermore, this alternative would be an extremely expensive solution, due to the costs

of the replacement (material and labour) and the expected downtime of the system. And finally it is

not sure whether the overall risk would be reduced through this measure because it cannot be

guaranteed that all necessary parts are replaced and hence the risk associated with corrosion could

not be eliminated completely.

Overall, the replacement of specific corrosion prone parts is not considered as an alternative.

6.3 Alternative 3: Substitution of sodium dichromate as corrosion inhibitor

Especially for the alternatives substances discussed in the following, the Arlanxeo AfA provides

extensive information, which due to the similarity of the AADC systems run by H&R and the more

general nature of the information available to date, can be considered valid for the present case as

well. According to the literature search conducted by H&R on the corrosion inhibitors, the alternative



43

assessment from Arlanxeo therefore still represents the latest stage of knowledge and development

(see Section 5.1.1).

The substitution of sodium dichromate by another corrosion inhibitor would be the most reasonable

alternative to the use of sodium dichromate. It is mandatory that the alternative corrosion inhibitor

entails similar inhibition functions as already discussed in Section 3.3. The main parameters, assessed

for corrosion inhibitor alternatives are corrosion resistance (effectiveness of the corrosion inhibitor)

at carbon steel, prevention of gas formation, and effectiveness at temperature ranges of 35–165 °C,

effectiveness at alkaline pH of approx. 9–12 and effectiveness in the absence of oxygen.

The suitability of the candidates for replacing sodium dichromate as corrosion inhibitor in AADC

systems identified in Chapter 5 are discussed in the following section based on specific criteria.

Generally, most of the effectiveness tests on alternative corrosion inhibitors are performed in vessels

in which a sample of the metal to be tested, typically carbon steel, is brought to a similar temperature

and pressure to those at the critical points of the absorption cycle, it is then left under these conditions,

measuring the corrosion gases which develop, and finally the sample surface is also analysed.

Simulation vessels are used for cost reasons, so that an entire machine incorporating an absorption

cycle does not have to be used, often for thousands of hours, at each test on a new corrosion inhibitor.

During years of testing new corrosion inhibitors, experience from companies from the refrigeration

sector that conducted numerous experiments both on test vessels and on actual machines

incorporating an absorption cycle clearly demonstrated that there is no simple relationship between

tests carried out in simulation vessels and those under real machine conditions. Generally, good

performance of a corrosion inhibitor in simulation vessels does not imply that it will operate well on

a real machine. Tests on simulation vessels can therefore be only used as preliminaries to select

families of corrosion inhibitors to be tested. Consequently, this analysis will focus on alternative

corrosion inhibitors that are tested on machines incorporating an ammonia water based absorption

cycles and not on simulation vessels.

6.3.1 Technical requirements for corrosion inhibitors at the applicants’ sites

A range of different parameters have to be regarded to ensure the efficiency and security of the AADC

systems operated by H&R in Hamburg and Salzbergen (Germany). This includes the following:

General process-related requirements

In AADC systems corrosion inhibitors are used to prevent corrosion induced metal loss that could

lead to critical system failures in cooling equipment like heat exchangers or recirculating water

piping. The loss of structural integrity, is of high concern, particularly for the high pressure

components of the system, such as the desorber and condenser. Furthermore, corrosion reduces

cooling efficiency due to gas formation and corrosion products may precipitate on critical heat

transfer devices and thereby insulate the metals.

The corrosion inhibitor must entail long-term activity and reliability of corrosion inhibition for carbon

steel over the whole life-time of the cooling unit which is for several decades.



44

Information requirements for a corrosion inhibitor change

Before an alternative corrosion inhibitor can be considered as alternative, different substance

information has to be available. This includes e.g. vapour pressure, solubility in ammonia water

mixtures, rectification, volatility, absorption, toughness, heat transfer, flow properties, etc.

Additionally, the stabilization of these parameters within the system ammonia/water over a long time

period has to be ensured. Corrosion test are often performed in a few days within autoclaves to

simulate AADC systems. These results are often not directly transferable to large-sized industrial

facilities with several MW cooling power. As mentioned in Section 5.2, a comprehensive

development has to be carried out before an alternative substance can be considered as safe and

reliable for the use as corrosion inhibitor in an AADC systems.

6.3.2 Assessment of alternative corrosion protective substances: Category 1

Corrosion inhibitor alternatives described within this AoA are divided into two groups: Category 1

and Category 2 alternatives. Category 1 comprises alternatives where initial R&D efforts ammonia

water based systems can be found. Although partly tested on test vessels or commercially available

small scale units, they are far away from being applied on the industrial scale. Respective R&D is

mostly of basic nature and ongoing.

Furthermore, the following assessment of the feasibility of the presented alternatives contains

summarizing tables with a colour code. The colours are as follows:

General information on the alternative substances assessed in Category 1 (e.g. physico-chemical

properties) and the respective categorisation regarding risk to human health and the environment is

provided in Appendix 2.

6.3.2.1 Molybdate compounds

6.3.2.1.1 Substance ID and properties

Molybdate is an anodic corrosion inhibitor that has been used for many years as corrosion inhibitor

for carbon steel. By precipitating an inert barrier layer (ferric molybdate) on the metal surface,

molybdate is able to suppress the anodic action. The protective layers, which are not chemically

bonded to the surface, can be resistant to flow velocity and turbulence. If used together with a nitrite

the anti-corrosive performance can be enhanced.

Colour Explanation

Not sufficient – the parameters/assessment criteria do not fulfil the requirements

The parameters/assessment criteria fulfilment not yet clear

Sufficient – the parameters/assessment criteria do fulfil the requirements

No data available



45

Molybdate also helps to retard pit growth due to the release of absorbed molybdate which

concentrates inside the pit precipitating as condensed molybdate species (GE Power & Water, Rey

and Thompson, 2013). Molybdates have not been used as extensively because they are weaker

oxidizing agents than chromates. In general, higher concentrations of molybdate are required to

achieve the comparable results (Patent, 1999).

Downey (1995) describes in a United States (US) patent the use of a complex mixture as working

fluid in absorption cooling systems. The working fluid consists of halogen or ammonium salts of

molybdenum, boron and, in a preferred embodiment, silicon added to the aqueous solution. A

hydroxide of sodium, lithium, potassium or ammonium is also added to attain the desired alkalinity.

The author claims that this mixture is an appropriate corrosion inhibitor for working fluids containing

aqueous solution of at least one compound selected from the group consisting of lithium bromide,

lithium chloride and lithium iodide. No further details are presented, especially no information about

the used system, test duration or any other information about corrosion inhibitor efficiency.

Phillips et al. (1996) describe in a US Patent corrosion inhibition of alkaline bases at 25 °C and

concentrations of 0.015 N and 0.2 N, as discussed in Section 6.3.2.5. The patent specification

discusses borates, molybdates and acetates as combination partners to strong alkaline bases.

6.3.2.1.2 Technical feasibility

Corrosion resistance: Beside the test results from the laboratory scale, as described in the several

patents, real-life experience exists for the use of molybdates in an ammonia/water based cooling

system. The experiences clearly demonstrate (as explained in Section 5.1.2) that the use of molybdate

as corrosion inhibitor caused severe corrosion in the cooling system.

Effective at alkaline pH: Molybdate inhibits steel corrosion in near neutral pH and alkaline media

(pH 6 and above). The pH range is described to be ideal in between 6–10.

Effective in absence of oxygen: Molybdate is not an effective corrosion inhibitor in the absence of

oxygen. The anti-corrosion performance on ferrous metals is based on the formation of a protective

oxide layer. It was stated that generally, for a good corrosion inhibition with molybdate an oxygen

concentration of at least 1 ppm is required. Molybdate ions react with the ferrous ions at the anodic

site to form a non-protective ferrous molybdate complex (Raheem 2011).

6.3.2.1.3 Economic feasibility

Based on the literature research and consultations, there is no indication that the discussed alternative

is not economically feasible. But it has to be taken into account that adverse interactions between the

current and the new (substitute) inhibition system may occur. So on one hand there are costs linked

Experience

at industrial

scale

Experience

at small scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

Temperatures

35-165 °C

Effective at

alkaline pH

(9-12)

Effective in

the absence

of oxygen



46

to the thorough replacement of the old inhibition system and on the other hand additional costs can

occur in case of unexpected interactions that impair the functionality of the inhibition system, as

unexpected corrosion leads to downtime of the AADC system and thus the wax and base oil

production. In any case, severe business impacts can be expected if the substitute inhibiton system

fails and a switch-back to sodium dichromate as corrosion inhibitor is not possible. To avoid this

scenario, the only solution is to replace the solution cycle equipment hardware to avoid any residual

“old” corrosion inhibitor, which of course comes with additional costs that need to be taken into

account.

6.3.2.1.4 Reduction of overall risk

As the alternative is not technically feasible, only classification and labelling information of

substances and products reported during the consultation were reviewed for comparison of the hazard

profile.

Based on the available information on the substances used within this alternative (see Appendix 2)

Ammonium molybdate constitutes the worst case with a classification as Acute Tox. 4, Skin Irrit. 2,

Eye Irrit. 2, STOT SE 3, Aquatic Chronic 3, Skin Sens. 1 and Resp. Sens. 1. As such, transition from

sodium dichromate – which is a non-threshold carcinogen – to one of these substances would

constitute a shift to less hazardous substances.

However, if molybdate compounds would be used as corrosion inhibitor in H&R’s AADC systems

there would be an increased risk of uncontrolled release of ammonia into the environment.

Availability


is not commercially available in appropriate amounts. However, the substance failed to prove suitable

performance for the safe and long-term use in AADC systems. Therefore, it is questionable if this

substance will be subject to further R&D. Generally, an extensive development process as described

in Section 5.2 would have to be passed successfully, before the substance could be reconsidered as

potential alternative.

6.3.2.1.5 Conclusion

In summary, molybdate compounds showed severe technical limitations in terms of corrosion

protection in AADC systems and effectiveness in the absence of oxygen. They cannot be considered

as an alternative corrosion inhibitor in AADC systems.

6.3.2.2 Sodium nitrite


Sodium nitrite (NaNO2) is one of the most commonly used anodic corrosion inhibitor shifting the

corrosion potential to more noble values and reducing corrosion current and can be seen as ‘true’



47

passivating agent, because it encourages formation of a passive layer on steel without itself being

involved in the film. Sodium nitrite requires a critical concentration for the protection of carbon steel.

Sodium nitrite is used as corrosion inhibitor in coolants consisting of utility water in cooling towers

in the presence of chlorine. Sodium nitrite requires nitrite levels that are at least equal to that of a

possible chloride concentration and should exceed potentially present sulphate levels. Such towers

often contain carbon steel pipes which have to be protected against corrosion. First studies indicate

that sodium nitrite could be a suitable corrosion inhibitor in ammonia water based cooling systems

(Hayyan et. al. 2012).

Nevertheless, sodium nitrite is no possible alternative for the use in AADC systems due to its

chemical reaction with ammonia as reducing agent.


The protecting film is formed through the adsorption of the nitride ions followed by an oxidation step

resulting in a very thin film of typically 2E-03 µm.

Corrosion resistance: Potentiostatic experiments could show that the corrosion potential values are

in general nobler than those obtained under identical conditions in uninhibited solutions. Sodium

nitrite is described as good anodic corrosion inhibitor (Hayyan et al, 2012). Nitrite was also tested in

commercially available small scale ammonia/water refrigeration systems, but turned out to be inferior

compared to chromates. Nitrites are rapidly consumed at higher temperatures and their protective

layer is far less efficient.

Prevention of gas formation: During the corrosion inhibition process with sodium nitrite, no gas

formation is associated according to Karim et al. (2010).

Effective at alkaline pH: Nitrites perform best corrosion inhibition in a pH range of 8-10 and should

not be used at pH below 7, which does not fit to the given pH-range in the AADC system of 9-12.

Often borate buffers are used in nitrite formulations to maintain a safe pH. Due to ammonia as cooling

agent there is an ammonium buffer system established in the cooling system, which might not be

compatible with a borate buffer system.

Effective in the absence of oxygen: Sodium nitrite acts as anodic corrosion inhibitor which attacks

directly corroding steel without requiring dissolved oxygen to form a protective oxide film, usually

magnetite (Fe2O4). In this respect sodium nitrite can be used as a corrosion inhibitor in closed systems

as described above.

Experience at

industrial

scale

Experience at

small scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

Temperatures

35–165°C

Effective at

alkaline pH

(9-12)

Effective in

the absence

of oxygen



48












account.

Reduction of overall risk



profile.


sodium nitrite represents the worst case with a harmonized classification as Ox. Sol. 3, Acute Tox. 3

and Aquatic Acute 1. As such, transition from sodium dichromate – which is a non-threshold

carcinogen – to one of these substances would constitute a shift to less hazardous substances.

However, if sodium nitrite would be used as corrosion inhibitor in H&R’s AADC systems there

would be an increased risk of uncontrolled release of ammonia into the environment.

Availability


is not commercially available in appropriate amounts. However, the substance failed to prove

sufficient performance already at small scale. Indeed, its capability for the safe and long-term use in

AADC systems is not proven. Therefore, it is questionable if this substance will be subject to further

R&D.


Sodium nitrite cannot be considered as suitable alternatives as it showed clear technical limitations

already in small scale applications. In summary, the substance cannot be considered suitable for the

given purpose.



49

6.3.2.3 Silicates/water glass


For many years, silicates have been used to inhibit aqueous corrosion, particularly in potable water

systems. Probably due to the complexity of silicate chemistry, their mechanism of inhibition has not

yet been firmly established. They appear to inhibit by an adsorption mechanism. It is thought that

silicates and iron corrosion products interact. However, recent work indicates that this interaction

may not be necessary.

Agrawal and Hindin described in 1993 experiments with several silicate compounds on test vessels

and on commercially available small scale refrigeration systems. Recently, Keller, J. (2014) describes

in the US patent US 2014/0091261A1 the use of water glass in ammonia absorption cooling systems.

The used sodium water glass consists of sodium oxide [Na2O, 6–8% weight by weight (w/w)], silicon

dioxide (SiO2, 25–30% w/w) and water (H2O, 62–69% w/w) (adjusted to 100%). Potassium water

glass was described with a comparable composition. Temperatures from 20–59 °C were tested with

1.5 to 4.5 mass-% of water glass added to the working fluid ('cooling medium'). The result indicates

that the mixture reduces corrosion in AADC systems and are hence described as chromate

substitutions.

Technical feasibility

Corrosion resistance/ Prevention of gas formation: Silicates are considered slow-acting corrosion

inhibitors; in some cases, 2 or 3 weeks may be required to fully establish protection. The protective

layer degrades over time and therefore a constant supply of silicate is said to be necessary (Asrar,

Malik and Ahmed, 1998).

Test in small scale refrigeration systems revealed that sodium silicate generated the same amount of

hydrogen as sodium chromate based systems. Tests were performed for 50 days within a temperature

range of up to 260°C. However, no further information is available if these systems perform in a safe

and reliable manner over long term in an industrial cooling plant.

The patent from Keller (2014) described the use of water glass in ammonia absorption cooling

systems. The used sodium water glass consists of sodium oxide (Na2O, 6–8% w/w), silicon dioxide

(SiO2, 25–30% w/w) and water (H2O, 62–69% w/w) (adjusted to 100%). Potassium water glass was

described with a comparable composition.

In several laboratory tests performed between 1999 and 2010 on six ammonia water based test

machines of the Platen-Munters type with a maximum power of 125 W, it was found that added basic

water glass acts as a corrosion inhibitor. When several test units were opened after far more than 10

years of continuous operation under full load, no traces of corrosion at all were found in the units.

The water glass added acts as a chemical buffer and ensures that the pH of the solvent remains high,

i.e., pH>11, even after many years of operation. Chemical analyses have also revealed that basic



50

water glass is not consumed over a period of time in contrast to the traditional Cr(VI) salts in the

solvent but instead is preserved. Water glass also seems to promote the formation of a thin inertizing

protective layer consisting essentially of magnetite crystals (Fe3O4), but also silicon in the interior of

the absorption equipment (Keller, 2014).

Operation in the temperature range of -35° C to 200° C was reported.

Effective in absence of oxygen: As mentioned above oxygen is essential for silicates to properly

function as corrosion inhibitors. As the AADC systems operated by H&R in Hamburg und Salzbergen

are designed as closed systems concentrations of dissolved oxygen are marginal. Oxygen levels of

5.5 ppm, as present in the above mentioned experimental setting of Asrar et al. (1998), do not occur.

Since oxygen – inter alia – is said to be a major factor regarding the corrosion inhibition properties

of sodium silicate for carbon steel the given inhibition efficiency can be expected to further drop

below 62 %.

However, the transformation of silicon into a metal silicate or silicon oxide depends on whether the

surrounding medium is aerated or not (Chen, J-R. et al., 1991).












account.




profile.

Experience

at industrial

scale

Experience

at small scale

Corrosion

resistance

Prevention of

gas

formation

Effective at

Temperature

s 35–165 °C

Effective at

alkaline pH

(9-12)

Effective in

the absence

of oxygen

Silicates/

waterglass

only

Silicates/

waterglass

only

Silicates/

waterglass

only



51


calcium metasilicate presents the worst case with a classification as Eye Irrit. 2, STOT SE3 and STOT

RE2. As such, transition from sodium dichromate – which is a non-threshold carcinogen – to one of

these substances would constitute a shift to less hazardous substances.

However, if silicates/water glass would be used as corrosion inhibitor in H&R’s AADC systems there

would be an increased risk of uncontrolled release of ammonia into the environment.

6.3.2.3.3 Availability


is not commercially available in appropriate amounts. R&D seems to be more advanced than for other

substances, first long-term testing results in ammonia/water based systems were performed. However,

as cooling capacity of industrial cooling plants like the AADC systems operated by H&R in Hamburg

and Salzbergen (Germany) is much higher than the here tested systems (xxxxxxxxxxxxxxxxxxxx),

these promising results cannot easily be adapted to large scale systems. Its capability for the safe and

long-term use in AADC systems has to be proven. Therefore, an extensive development process as

described in Section 5.2 has to be carried out, before the substance could be considered as potential

alternative.


As of today, the tested corrosion inhibitor systems cannot be considered as suitable alternatives as

there long-term performance in industrial scale has not been proven yet. Further R&D is necessary to

deeper evaluate whether a silicates/water glass based corrosion inhibitor system can be considered as

replacement corrosion inhibitor. To pass a whole development cycle, at least 9-15 years are necessary

if no major drawbacks occur.

6.3.2.4 Zinc containing corrosion inhibitors


Zinc is used as corrosion inhibitor in various technological fields, including cooling systems. Zinc is

relatively insoluble due to the precipitation of zinc hydroxide whose solubility product (Ksp) is 1.2E-

17. Aqueous solutions with pH > 7.8 contain remarkable concentrations of hydroxide ions which

rapidly increase as the pH rises. Hence, the zinc solubility decreases drastically with increasing pH.

At the cathodic side oxygen is reduced and hydroxide ions are formed. This locally high hydroxide

concentrations cause zinc to precipitate at the cathodic side passivating it with a zinc hydroxide

inhibition film interrupting the redox reaction effectively while minimizing the reaction at the anode

where the metal loss occurs. Therefore, zinc itself belongs to the group of precipitating cathodic

corrosion inhibitors. Mostly common used are zinc sulphate or chloride (Young, T. 1991). Zinc

phosphate is even less soluble [Solubility product (Ksp) = 9.1E-33) than zinc hydroxide. The main

limitation of zinc based corrosion inhibitors are seen in the fact that only local precipitation of zinc

hydroxide at the metal surface to protect is desired, whereas an uncontrolled precipitation would cause

severe problems within the AADC systems.



52

Zinc is usually not used alone, but in combination with several other substances as stated in scientific

literature (e.g. Rose et al, 2009; Rajendran et al, 2000, 2003 and 2012; Florence et al, 2005). However,

the usability of zinc mixtures under specific conditions differs according to the synergists’ properties

within the mixed corrosion inhibitor system. These corrosion inhibitors deposit at a pH range of

typically 7-9. Zinc can precipitate as hydroxide, carbonate or phosphate. The chemistry relies on

cathodic corrosion inhibition by zinc, coupled with anodic corrosion inhibition by orthophosphates

(Young, T. 1991; GE Power & Water 2013).

The use of zinc compounds for corrosion inhibition in an ammonia water based system is also

described in a US patent by Agrawal and Hindin (1993). Guerra, M. (2003) describes in an EU patent

application a mixture of KOH, KNO3 and ZnO-3B2O3, as corrosion inhibitor added to the working

fluid ('cooling medium') of a small scale ammonia water based absorption refrigerator. Tests were

performed in commercially available refrigerators for the time of 169 days. However, this patent was

withdrawn in 2009 [Reason according to European Patent Office (EPO) register: examination fee not

paid in time].


Corrosion resistance: In numerous studies corrosion inhibition efficiencies of several zinc based

systems were tested in the laboratory scale as revealed by weight loss experiments. In these

experiments, zinc based systems + additives were tested for their corrosion inhibition effectiveness

on different kinds of steel for varying exposure times. These experiments already showed that

inhibition efficiencies for zinc based systems are pH dependent and are clearly not comparable to

sodium dichromate.

Prevention of gas formation: In the US patent by Agrawal and Hindin (1993) sodium zincate was

tested in commercially available ammonia/water cooling systems for residential use. After 60 days

for the sodium zincate inhibited system hydrogen formation, as a clear sign of corrosion, was

observed at a rate almost 20 times greater than the chromate inhibited cooling system.

In an EU patent (Guerra, 2003), a zinc based system was tested in different small scale ammonia

absorption cooling systems and was considered as promising. After 169 days of testing,

incondensable gas values around 0.1–0.2 ml/hour were observed. However, no long term experience

exists with this zinc based system. Interestingly, the patent was withdrawn in 2009. Furthermore, the

borate compound used within this mixture gives rise to concern, as borates have been identified as

SVHC.

Effective at alkaline pH: Zinc salts in general are described to be effective in the pH range of 6.5 to

8.5. Hence, they are not considered as feasible for the AADC systems operated by H&R in Hamburg

and Salzbergen (Germany) which have a higher alkaline pH range of approx. 9 to 12.

Although the suitability depends on the system of substances used with zinc the formation of zinc

hydroxide is highly problematic in basic pH ranges. Solubility of zinc hydroxide dramatically drops

between pH 7 and 9 (Reichle, McCurdy & Hepler, 1975). Occurring deposits of precipitated zinc

hydroxide may cause complications within the cooling system.



53

Under the given circumstances in the AADC systems operated by Hamburg and Salzbergen

(Germany), especially with the given alkaline pH between 9 and 12, it can be expected that zinc will

precipitate as hydroxide within the system. This precipitation is different from the desired

precipitation process at the cathodic side, because immediate local precipitation of zinc hydroxide at

the place where the substance is added can be assumed. The hydroxide would potentially circulate as

solid matter within the closed cooling system.

Based on scientific literature and patents, it can be concluded that none of the zinc containing mixtures

is a suitable alternative to sodium chromate as corrosion inhibitor.



is not economically feasible. But it must be taken into account that adverse interactions between the









account.




profile.

Based on the available information on the substances used within this alternative (see Appendix 2),

boron trioxide (B2O3) constitues the worst case with a classification as Acute Tox. 4, Skin Corr. 1B,

Aquatic Chronic 1 and Aquatic Acute 1. As such, transition from sodium dichromate – which is a

non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous

substances.

However, if zinc containing corrosion inhibitors would be used in H&R’s AADC systems there would

be an increased risk of uncontrolled release of ammonia into the environment.

Experience

at industrial

scale

Experience

at small scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

Temperatures

35–165 °C

Effective at

alkaline pH

(9-12)

Effective in

the absence

of oxygen



54

Availability


is not commercially available in appropriate amounts. However, its capability for the safe and long-

term use in AADC systems is not yet proven. Therefore, an extensive development process as

described in Section 5.2 must be carried out, before the substance could be considered as potential

alternative.


In one patent (Guerra, M., 2003), a zinc containing mixture showed promising results in small scale

refrigeration systems. However, this patent was withdrawn in 2009 (Reason according to EPO

register: examination fee not paid in time). In summary, the tested zinc containing corrosion inhibitor

systems cannot be considered as suitable alternatives as they showed technical limitations already at

laboratory and in small scale applications. Furthermore, its capability for the safe and long-term use

in AADC systems is not yet proven. In summary, the substance cannot be considered suitable for the

given purpose.

6.3.2.5 Strong alkaline solutions

6.3.2.5.1 Substance ID and Properties

Several patents describe the use of alkaline solutions for corrosion inhibition in ammonia water based

systems. In a US patent from Phillips et al. (1996), a method of inhibiting corrosion and the formation

of hydrogen is described in ammonia water based absorption cooling, air conditioning or heat pump

system by maintaining the hydroxide ion concentration of the aqueous ammonia working fluid, within

a selected range under anaerobic conditions at temperatures up to ca. 218 °C (425° F). Erickson D.C.

(1999) describes a method of corrosion inhibition in an aqueous ammonia absorption refrigeration

apparatus based on an alkali metal base. A process for controlling corrosion and hydrogen generation

in the aqueous ammonia absorption cycle apparatus is also disclosed. Variations have been tested,

including NaOH, LiOH, KOH, RbOH, CsOH and GeO2 as additive. Guerra, M. (2003) describes in

an EU patent application a mixture of KOH, KNO3 and ZnO-3B2O3, as corrosion inhibitor added to

the working fluid ('cooling medium') of a small scale ammonia water based absorption refrigerator.

Tests were performed in commercially available refrigerators for the time of 169 days. It is of note

that the aforementioned patents are expired meanwhile, as the maintenance fees were not paid.


Corrosion resistance/ Prevention of gas formation: In most patents an experimental corrosion test

apparatus was used instead of small scale systems that are used in real life. The test apparatus was

designed to operate at conditions simulating those in the hottest part of the generator, and has boiling

surfaces, peak temperatures that accelerate the corrosion reactions, and a recirculating ammonia water

based working fluid ('cooling medium'). The test was performed for approximately 1 year. The

corrosion inhibition capabilities have been described as appropriate. Examples of strong bases

suitable for use include, alkali metal bases, such as sodium hydroxide, potassium hydroxide, lithium



55

hydroxide and caesium hydroxide. Preferably, the strong base is lithium hydroxide, or sodium

hydroxide.

The EU patent (Guerra, 2003) reported the testing of several corrosion inhibitors also those described

in the aforesaid previous patents. Guerra et al. tested these on real machines, with the discovery that

they are much less effective than the corrosion inhibitors claimed as follows: a zinc based system

with KOH as additive in different small scale ammonia absorption cooling systems was considered

as promising. After 169 days of testing, incondensable gas values around 0.1–0.2 ml/hour were

observed. However, no long term experience exists with these system. In contrast, when known

refrigerator units were tested with KOH only, gas formation was remarkably high and the

performance clearly insufficient. Interestingly, the patent was withdrawn in 2009.

Effective at 35–165 °C: The literature indicates that the alternative is working at high temperatures

(<218° C). Only Guerra tested in real small scale systems, demonstrate that alkaline systems alone

did not work properly, while performance could be improved when using an alkaline zinc borate

based systems. No experience exists on the large temperature differences as present in AADC

systems.

Effective at alkaline pH: The literature indicates that the alternative is appropriate in the given pH

range.



is not economical feasible. But it has to be taken into account that adverse interactions between the









account.




profile.

Experience

at industrial

scale

Experience

at small scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

Temperatures

35–165 °C

Effective at

alkaline pH

Effective in

the absence

of oxygen



56

Based on the available information on the substances used within this alternative (see Appendix 2),

KOH constitute the worst case with a classification as STOT SE3, Skin Irrit. 2 and Eye Irrit 2. As

such, transition from sodium dichromate – which is a non-threshold carcinogen – to one of these

substances would constitute a shift to less hazardous substances.

However, if strong alkaline solutions would be used as corrosion inhibitor in H&R’s AADC systems


Availability



term use in AADC systems is not proven. Therefore, an extensive development process as described

in Section 5.2 must be carried out, before the substance could be considered as potential alternative.


Test performed with alkaline corrosion inhibitor systems in general were clearly found to be

insufficient. In one patent (Guerra, M., 2003), an alkali based zinc borate containing mixture showed

promising results in small scale refrigeration systems. However, this patent was withdrawn in 2009

(Reason according to EPO register: examination fee not paid in time). In summary, the tested

corrosion inhibitor systems cannot be considered as suitable alternatives as they showed technical

limitations already at laboratory and in small scale applications. Furthermore, its capability for the

safe and long-term use in AADC systems is not yet proven. In summary, the substance cannot be

considered suitable for the given purpose.

6.3.2.6 Phosphates and phosphonate compounds


For corrosion inhibition in cooling systems, several phosphates based corrosion inhibitor systems are

discussed in scientific literature. Trisodium phosphate (Na3PO4) are used in industrial cooling water

systems as antiscalants, which can positively influence the corrosion rate. The primary reactant for

carbon steel corrosion inhibition is oxygen, due to the formation of a thin oxygen film. The dissolved

oxygen produces a thin film of γ-Fe2O3, where the phosphate ions fill in the voids and accelerate film

growth. These plugs prevent further diffusion of Fe2+ ions from the metal surface. If these complexes

are hydrolysed this leads to local attacks by the production of acid domains.

Phillips et al. (1996) describe in a patent specification phosphate as possible “unfavourable” corrosion

inhibitors for ammonia water based cooling systems. Hindin et al. (1992) describe in a patent

specification different substances, including sodium phosphate (Na3PO4) as possible corrosion

inhibitors for ammonia water based systems. Hindin concludes that phosphates lead to a worse

Inhibition Efficiency (IE) compared to other substances tested.

In combination with zinc, a NaZnPO4 film can be built whereas the Zn2+ ion binds to any two adjacent

oxygen atoms. Inhibition may be caused by the stabilization of the surface film in form of an iron

complex (NaFePO4) which is more stable than a zinc film (NaZnPO4). The iron complex provides



57

anodic corrosion protection whereas formation of insulated film of zinc hydroxide [Zn(OH)2] at

higher pH levels provides cathodic corrosion protection.

Phosphonates and phosphonic acids are organophosphorus compounds containing carbon-bonded

PO(OH)2 or PO(OR)2 groups (where R = alkyl, aryl). Phosphonates as organic phosphorous

compounds can be distinguished from inorganic polyphosphates in that all phosphonates contain

direct carbon-phosphorous bonds. Phosphonates are used in cooling water treatment to control

calcium carbonate scale. Additionally, they possess corrosion inhibition properties. Phosphonates

belong to the precipitating corrosion inhibitors which are protecting both anodic and cathodic sites

by the precipitation of calcium and iron salts forming protective films. For carbon steel protection,

Hydroxy Phosphonic Acid (HPA) was specifically designed as corrosion inhibitor. When used alone,

HPA crucially needs calcium in water for effective protection of carbon steel. A general problem with

phosphonates is their decomposition over time to orthophosphates which are poor corrosion

inhibitors. This reversion is increased by high and low pH, high temperature and the presence of

oxidisers like chlorine or bromine. Studies indicate that phosphonates are effective corrosion

inhibitors for carbon steel when combined with zinc (NISCAIR, GE Power & Water 2013, Rao

B.V.A., et al 2013).


Corrosion resistance: Phosphate stabilized inhibition systems are able to prevent corrosion but to a

far less extent as chromate/zinc based systems. Under operating conditions as described for

ammonia/water systems, this replacement technology is clearly insufficient.

Prevention of gas formation: The passivating process induced by phosphate ions is based on the

production of a protective Fe2O3 layer. During this process hydrogen is generated.

Effective at temperatures 35–165 °C: Tests with phosphates and orthophosphates in carbon steel at

temperatures of 20-80 °C showed and insufficient performance. The solubility of the passivating layer

increased within the tested temperature range (Kilinççeker et al, 1999; Pryor and Cohen, 2001). As

H&R’s cooling systems operate at temperatures up to 165 °C, phosphates do not constitute a suitable

alternative.

Effective at alkaline pH: Phosphate is used primarily in zinc based cooling water corrosion protection

systems that will be operated at a pH of 8.5 or less. The inclusion of phosphate, normally as

orthophosphate, to zinc containing corrosion inhibitory solutions at lower pH result in the formation

of mixed zinc hydroxide/phosphate protective films at the cathode. At relatively high pH tested (pH

7.2 and pH 12.3) it could be shown that phosphate ions in combination with sulphate ions have an

increased capability of corrosion inhibition than phosphate alone and give an overall corrosion

protection (Kilinççeker et al, 1999; Raheem, 2011; Armstrong et al, 1994).

Effective in absence of oxygen: It is assumed that oxygen dissolved in solution is a main reason for

generating a passivation layer due to a heterogeneous reaction of phosphates with surface iron atoms

forming Fe2O3. Sodium phosphate is described as corrosion inhibitor that essentially requires oxygen

for its passivating activity (Pryor and Cohen, 2001).



58

In summary, any of the tested phosphate compounds showed severe limitations in terms of the key

requirements as concluded in the table below. Most importantly, they are not able to provide the same

level of corrosion resistance as sodium dichromate and are therefore no alternative in AADC systems.












account.




profile.

Based on the available information on the substances used within this alternative, trisodium phosphate

(see Appendix 2) would represent the worst case with a classification as Skin Irrit. 1, Eye Irrit. 1,

STOT SE3, Skin Corr. 1C. As such, transition from sodium dichromate – which is a non-threshold

carcinogen – to one of these substances would constitute a shift to less hazardous substances.

However, if phosphates and phosphonate compounds would be used as corrosion inhibitor in H&R’s

AADC systems there would be an increased risk of uncontrolled release of ammonia into the

environment.

Availability



term use in AADC systems is not yet proven. Therefore, an extensive development process as

described in Section 5.2 has to be carried out, before the substance could be considered as potential

alternative.

Experience

at industrial

scale

Experience

at small scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

Temperatures

35–165 °C

Effective at

alkaline pH

Effective in

the absence

of oxygen



59


In summary, any of the tested phosphate compounds showed severe limitations in terms of the key

requirements already at laboratory scale. They are not able to provide the same level of corrosion

resistance as sodium dichromate and are therefore no alternative in AADC systems.

6.3.2.7 Rare Earth Metal Salts

6.3.2.7.1 Substance ID and Properties

Rare Earth Metal Salts (REMSs) are described in the literature and patent specifications as suitable

corrosion inhibitor for substrates such as aluminium alloys, steel and zinc.

In several publications and a US patent Mansfeld, F. B. (2003) described the use of cerium nitrate

[Ce(NO3)3] which is add to the ammonia water based working fluid in a heat pump to inhibit corrosion

of the steel surfaces. Concentrations REMS is reported to be between 10 mM to 350 mM. Cerium is

expected to act by steel surface passivation due to oxide/hydroxide layer formation.

Carbon steel can be coated with cerium, assisted by hydrogen peroxide (H2O2) resulting in a layer

that provides corrosion inhibition. Nevertheless, to use hydrogen peroxide in the closed AADC

systems operated by H&R in Hamburg and Salzbergen would lead to undesired gas formation.


In the existing studies and patents, REMSs were tested on steel plates in test vessels for up to 48 h.

None of these tests were performed on real scale systems. Importantly, the patent where these

interventions are described expired due to failure of maintenance fee 5 years after assignment of the

patent. In summary, no reliable studies or experiences exist that REMSs are a potential alternative as

corrosion inhibitor in AADC systems.



is not economical feasible. Nevertheless, prices for pure cerium as rare earth metal are relatively high.

But it has to be taken into account that adverse interactions between the current and the new

(substitute) inhibition system may occur. So on one hand there are costs linked to the thorough

replacement of the old inhibition system and on the other hand additional costs can occur in case of

unexpected interactions that impair the functionality of the inhibition system, as unexpected corrosion

leads to downtime of the AADC system and thus the wax and base oil production. In any case, severe

business impacts can be expected if the substitute inhibiton system fails and a switch-back to sodium

Experience

at industrial

scale

Experience

at small scale

Corrosion

resistance

Prevention

of gas

formation

Effective at

Temperatures

35–165°C

Effective at

alkaline pH

Effective in

the absence

of oxygen



60

dichromate as corrosion inhibitor is not possible. To avoid this scenario, the only solution is to replace

the solution cycle equipment hardware to avoid any residual “old” corrosion inhibitor, which of

course comes with additional costs that need to be taken into account.




profile.


cerium trinitrate represents the worst case with a classification as STOT SE3, Skin Irrit. 2 and Eye

Irrit 2. As such, transition from sodium dichromate – which is a non-threshold carcinogen – to one of

these substances would constitute a shift to less hazardous substances.

However, if rare earth metal salts would be used as corrosion inhibitor in H&R’s AADC systems


Availability



term use in AADC systems is not proven. So far, not even tests in small scale were performed.

Therefore, an extensive development process as described in Section 5.2 has to be carried out, before

these substances could be considered as potential alternatives.


The tested corrosion inhibitor systems cannot be considered as suitable alternatives as they showed

technical limitations already at laboratory and in small scale applications. Furthermore, its capability

for the safe and long-term use in AADC systems is not yet proven. In summary, the substances cannot

be considered suitable for the given purpose.



61

7. OVERALL CONCLUSION ON SUITABILITY AND AVAILABILITY OF

CORROSION INHIBITOR ALTERNATIVES

H&R uses sodium dichromate as a corrosion inhibitor in two AADC systems operated at their sites

in Hamburg and Salzbergen (Germany). For many decades, AADC systems made of carbon steel

have constituted a safe and reliable cooling technology for miscellaneous industry sectors. This was

ensured by using sodium dichromate as a corrosion inhibitor, enabling high performance under

specific process conditions. For the purpose of this AoA, different chemical and technical alternatives

have been evaluated.

Three different alternatives were discussed:

1. The replacement (change) of the existing AADC system by switching to VCC as an alternative

cooling technology, described in Section 6.1. Even though technically feasible, the switch

would be accompanied with severe economic impacts. A switch to VCC would in H&R’s case

amount to net economic impacts of EUR 40 million (considering investment in a new cooling

system, value added forgone due to downtime and additional operational costs), which in total

points against this alternative today. More detailed calculations are provided in the SEA

document.

2. As described in Section 6.2, the replacement of corrosion prone parts, mainly carbon steel

parts by more resistant parts, e.g. stainless steel or permanently coated metal parts is another

potential alternative. From a technical and economic point of view a replacement of corrosion

prone parts cannot be considered as suitable. As of today, no standard or best-practice solution

is applicable for H&R’s sites in Hamburg and Salzbergen (Germany). It was highlighted that

stainless steel systems of a similar size to H&R’s systems are currently not operated and no

reliable conclusion about the presence or absence of corrosion inhibitors in such systems can

be drawn. It was also clearly outlined, that stainless steel is subject to corrosion in ammonia

water based systems, especially at higher temperatures. It was also recommended by

specialists that in this case sodium dichromate should be used as only long-term proven

corrosion inhibitor. Therefore, from a technical perspective, the exchange of corrosion prone

parts cannot be considered as a suitable alternative.

3. The substitution of sodium dichromate by another corrosion inhibitor would be the easiest and

cheapest alternative. It is described in Section 6.3. Extensive efforts were made during the last

years to identify possible alternatives for corrosion inhibitors in AADC systems. Over the

course of these efforts, scientific literature was screened and evaluated comprehensively.

Experts from other companies dealing with similar cooling systems were approached.

Moreover, several other international research institutes were contacted to discuss and

evaluate the state of the art for corrosion inhibition in this type cooling systems.

The analysis revealed that there is limited available experience on replacement substances for

large scale industrial cooling systems. As of today, no drop-in alternative to sodium

dichromate for the use as a corrosion inhibitor in AADC systems is available.



62

AADC systems made of carbon steel have been used as a safe and reliable cooling technology

for decades. Using sodium dichromate as a corrosion inhibitor ensures a long-lasting life time

of the cooling plants (up to 50 years). Indeed, scientific and technical research was performed

over decades suggesting a variety of replacement corrosion inhibitors. Nevertheless, all

alternatives discussed in scientific and technical literature were not tested under realistic

conditions in large-scale systems for a realistic time span. Therefore, no replacement

substance could be identified. For the development and industrial upscaling of a possible

alternative for sodium dichromate as a corrosion inhibitor in AADC systems made of carbon

steel several phases, bringing an alternative step by step to final application would be

necessary. The integrity and reliability of the system must be ensured over the expected

lifetime of the facility. Unexpected corrosion would lead to system downtime associated by

immense costs and a reduced environmental and occupational safety. In this context, it would

be unjustifiable to simply start a substitution in form of a field trial without having enough

scientific and empirical data about the safe use of such alternatives.

As clearly outlined in Section 5.2, passing the whole development and implementation process plus

the required monitoring will easily take 20 years. Taking into account the limited worker exposure to

sodium dichromate in combination with extremely high occupational safety measures (see CSR), the

resulting considerable low health impacts (under existing conditions there is no concern and

negligible risk for workers and the environment) and the comparably high economic impacts (see

SEA), the most reasonable option is to run the AADC systems operated by H&R until the end of their

expected lifetime (20 and 35 years from now). Therefore, H&R applies for a review period of 20

years for the use of sodium dichromate.



63

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67

APPENDICES

Appendix 1 - Category 2 alternatives

Alternative Substance properties Feasibility

Amines

Amine based corrosion inhibitors are

commonly used in industrial

lubricants, greases and rust-

preventive fluids. Typical amine

based corrosion inhibitors are:

ammonia, dimethylethanolamine,

ethylenediamine,

methoxypropylamine,

monoethanolamine, morpholine,

picolines and amines. They are used

as corrosion inhibitors in the oil and

gas industry, where they support the

inhibition of corrosion induced by

hydrochloride in connection with

water. For that purpose, ammonia has

been widely used for decades.

Amines are often used in de-aerated

NaCl containing aqueous solutions.

Studies describe amine based

corrosion inhibitors as active due to

physical adsorption on the metal

surface (Buchweishaija, 2002).

Hydrazine (N2H4) is described as

possible corrosion inhibitor which

does not act as an electrochemical

type corrosion inhibitor. Instead it

decreases corrosion potential by the

reduction of oxygen present in the

fluid, which leads to the formation of

water and nitrogen. Usually hydrazine

is used as an additive to boiler feed

water (Petersen et al., 2014).

Formulations based on dilute aqueous

solutions of N,N′-

Dimethylethanolamine (DMEA) are

used to protect reinforcement steel

bars (‘rebar’) in concrete from

corrosion. DMEA is a widely

common corrosion inhibitor often

used to protect iron in concrete and in

alkaline and chlorine containing

solutions. Studies described DMEA

Corrosion resistance is described to be

very good and IE accordingly high.

Oxygen is generally removed by

reductive corrosion inhibitors such as

amines and hydrazines according to

the following equation: O2 + N2H4

→ 2 H2O + N2, and therefore the

corrosion inhibition mechanism of

hydrazines bases on the removal of

oxygen under the release of gaseous

nitrogen.

DMEA as corrosion inhibitor is

studied and reported in scientific

literature. The assessed reports

describe DMEA as corrosion

inhibitory active in the presence of

NaCl and at acidic pH.

Studies evaluated describe DMEA as

active at temperatures of around

25 °C.

Hydrazine has been identified as

SVHC for its cancerogenic

properties. Hydrazine is classified as

Flam. Liq. 3 and its usability within

the H&R’s facilities would lead to

additional chemical hazards.

In summary, the key requirements for

corrosion inhibitors in terms of suitability

to alkaline pH, closed circuits, hot and

chilled water systems may be fulfilled by

amines. Nevertheless, the inhibition

mechanism depends on the formation of

nitrogen gas. Additionally, its capability

for the safe and long-term use in AADC

systems is not yet proven. Therefore,

these substances are not regarded as an

alternative to sodium dichromate.



68


alone as unsuitable corrosion

inhibitor for carbon steel, but as

acceptable in combination with

caprylic acid. The mechanism of

organic corrosion inhibitors is not

clear but it is assumed that DMEA

displaces chloride ions and forms a

passivating film on the metal surface.

Tartrate

compounds

According to literature, tartrate

compounds are often used as

synergist in combination with other

substances for corrosion inhibition in

liquid media. Corrosion inhibition

effects of sodium potassium tartrate

and Zn2+ mixtures for example could

be shown for carbon steel immersed

in rain water.

The substance is known as corrosion

inhibitor for aluminium and carbon

steel alloys. Here it provides good

inhibition efficiency as anodic

corrosion inhibitor and in

combination with zinc ions mixed

corrosion inhibitor properties. Also

sodium potassium tartrate in

combination with zinc show

synergistic effects in controlling the

corrosion of carbon steel. Studies

showed such effects for carbon steel

immersed in rain water collected from

roof top and stored in concrete tanks.

91 % corrosion IE was measured for a

formulation consisting of 50 ppm

sodium potassium tartrate and 25 ppm

zinc (NISCAIR).

According to the CRC Handbook of

Chemistry and Physics (84th edition,

Boca Raton, FL: CRC Press Inc.,

2003-2004, p. 4-85) the melting point

of potassium sodium tartrate is

130 °C and the decomposition

temperature 220 °C. Due to the low

boiling and decomposition point it

can be assumed that the substance

may lead to gas formation in parts of

the cooling unit with higher

temperature.

So far no scientific information about

the temperature range for proper

functioning of the substance could be

identified. Due to the relatively low

boiling (ca. 130 °C) and

decomposition (ca. 220°C) point

tartrate is considered as not suitable

at higher temperatures.

The corrosion inhibitor system acts as

a mixed type corrosion inhibitor and

could be shown to be effective in the

pH range 6-8. Electrochemical

impedance studies indicated the

formation of a dense protective film

which is only protective in the

presence of optimum amounts of the

above mentioned compounds at a

given pH value (Rao et al., 2013).





tartrate compounds according to the

literature. However, its capability for the

safe and long-term use in AADC systems

is not yet proven. Therefore, a detailed



69


R&D process including long-term testing

on pilot scale and further industrial

upscaling have to be performed before the

final performance of tartrate compounds

can be assessed ultimately.

Benzoate

Sodium benzoate (NaC7H6O2) is used

as corrosion inhibitor for different

uses including carbon steel. The main

factors affecting corrosion inhibition

of iron in sodium benzoate solutions

are the concentration of benzoate, the

pH of the solution and the dissolved

oxygen concentration (Davieset al.,

1973).

Sodium benzoate is described to show

corrosion inhibition potential for

carbon steel. It has been shown to be

an effective inhibitor of the corrosion

of mild steel in distilled water, in

moderately hard mains-water and very

dilute (e.g. 0.03 %) sodium chloride

solutions. Sodium benzoate is

described as less efficient than sodium

chromate but it is, however, named

‘safe inhibitor’ since it does not lead

to intense localized corrosion when

the concentration is just below the

minimum for protection. Furthermore,

the efficiency is higher at clean

surfaces and is decreased with time in

stationary and flow conditions

(Hassan et al., 2011).

Sodium benzoate corrosion inhibition

is reported as effective at

temperatures of 30 – 50 °C.

(Wormwell and Mercer 1952, Ivušić

et al., 2014). Further information

about higher temperatures could not

be identified





sodium benzoate according to the

literature. However, the corrosion

inhibition capacity is described to

decrease with increasing velocity. Due to

the high velocity of the AADC system

this alternative is considered to be not

appropriate. Furthermore, its capability


systems is not yet proven. Therefore, a

detailed R&D process including long-

term testing on a pilot scale and further

industrial upscaling have to be performed



70


before the final performance of benzoates

can be assessed ultimately.

Glutamate

Mono Sodium Glutamate (MSG)

(NaC5H9NO4) in combination with

zinc show synergistic effects as a

mixed corrosion inhibitor system

used for carbon steel as underpinned

by polarisation studies. AC

impedance spectra reveal a protective

film formed on the metal surface. FT-

IR spectra indicate that the protective

film consists of Fe2+-MSG complex

and Zn(OH)2 (Leema Rose et al.,

2009).

A formulation of 100 ppm MSG and

50 ppm Zn2+ shows an IE of 86 %

which increases with pH. Studies

reveal that for this mixture the

acceptable pH is around the neutral

point, which in turn is below the pH

of AADC systems (Leema Rose et

al., 2009).

Furthermore, increasing (alkaline) pH

holds negative influence on the

inhibition efficiency of MSG-Zn²+

systems (Leema Rose et al., 2009).




chilled water systems are not fulfilled by

glutamate. Furthermore, its capability for

the safe and long-term use in AADC

systems is not determined. Therefore, the

substance is not considered as an

alternative to sodium dichromate.

Succinic

acid

Succinic Acid (SA) is a dicarboxylic

acid, which is most commonly known

for its role in the citric cycle of

intermediary metabolism. Besides

various applications e.g. in food,

pharmaceuticals, agriculture and

industry SA is known to possess anti-

corrosive properties. Therefore it is

used e.g. for coatings and in water

cooling systems (Chemicalland 21,

2015). The corrosion inhibitory effect

of organic substances like SA is

explained by adsorption of the agent

to the metal surface resulting in a

protective film that prevents

corrosion by separating the metal

surface and the electrolyte (Dariva

and Galio 2014).

In this context SA is often used in

combination with other agents like

zinc or is part of a whole series of

ingredients in mixtures of anti-

corrosive products. Nevertheless,

Studies revealed the role of SA as

anodic-type corrosion inhibitor on low

carbon steel in an aerated, non-stirred

environment, with acidic pH (1.0 M

HCl) in the range of 2 - 8 at 25 °C.

Negative effects of increasing

temperature on the corrosion

inhibition properties of SA concerning

carbon steel were observed. A shift in

the corrosion inhibitory effect might

be a severe disadvantage for an

application of SA in the given

temperature range of the production

process (Deyab and Abd El-Rehim

2013).

There is evidence that in combination

with carbon steel, the performance of

SA as corrosion inhibitor is a

function of the agent concentration.

An optimum was detected at a

concentration of 50 ppm SA at pH 3.

This indicates that the pH in the

AADC system might be too high to



71


there is evidence on the use of mere

SA as an anti-corrosive substance.

guarantee proper corrosion inhibition

by SA.

In contrast to the above mentioned the

literature review yielded results

indicating corrosion inhibition of SA

at pH 12 but for aluminium as the

substrate to be protected and only for

SA in combination with other

chemicals (Deyab and Abd El-

Rehim, 2013, Rajendran et al., 2012).

Based on the available information on

the substances used within this

alternative, SA would be the worst

case with a classification as Muta. 1B

and Carc. 1B. As such, transition

from sodium dichromate – which is a

non-threshold carcinogen – to one of

these substances would not constitute

a shift to less hazardous substances




chilled water systems is not fulfilled by

SA. Especially the pH range reported in

the literature is not appropriate for the

given use in AADC systems.

Additionally, its capability for the safe

and long-term use in AADC systems is

not yet proven. Therefore, the substance

is not considered as an alternative to

sodium dichromate.

Organic

inhibitors

The field of organic corrosion

inhibitors is very heterogeneous. The

mode of action is based upon

cathodic and anodic inhibition

schemes or a coupling of both. But in

general, organic inhibitors establish

protective layers on the surface of the

substrate (Dariva and Galio, 2014).

Due to the importance of this

corrosion inhibitor class - literally

often claimed as ‘environmental

friendly’ - some substances which are

not separately discussed within this

AoA are summarized here. Various

organic compounds are used as

Sekine at al. (1992) indicate the use of

several organic polymers, such as

polymaleic acid derivative (PMAD),

polyacrylic acid derivative (PAAD)

or polyacrylic acid (PAA), for

corrosion inhibition in cooling water

systems. Thereby, only anionic

polymers are considered to be

effective due to the adsorption to the

metal surface and subsequently the

formation of a protective layer.

According to Samide et al. (2005) N-

cyclohexyl-benzothiazolesulfenamide

(NCBSA) is effective in inhibiting

corrosion of carbon steel in ammonia

solutions at room temperature by



72


corrosion inhibitors. Some of them

are already discussed in other

sections. Organic inhibitors usually

contain heteroatoms, often nitrogen

groups, such as amines or sulphur or

hydroxyl groups often as surfactants

with dual functionality. Contained

hydrophilic group can adsorb on the

metal surface, and an opposing

hydrophobic group prevents further

wetting of the metal. Size,

orientation, shape, and electrical

charge distribution of the molecules

are important factors for the corrosion

inhibition efficiency. Glycine

derivatives and aliphatic sulfonates

are examples of compounds which

can function in this way (Dariva and

Galio, 2014).

All-organic corrosion inhibitory

programs are frequently used in

systems without pH control and they

rely on systems that have a tendency

to form scale as opposed to corrosion.

All-organic programs are normally

not used in aggressive waters. Some

companies offer corrosion inhibitors

under various trade names, as for

example HALOX® organic corrosion

inhibitors which are described to be

effective against flash rusting and in-

can corrosion prevention. The

corrosion inhibitors are described to

be suitable for high gloss, thin film,

and clear coat applications (ICL,

2015; Palou et al., 2014; Rani and

Basu, 2012).

adsorption of the compound on the

metal surface.

Glycine derivatives and aliphatic

sulfonates, as a group of organic

corrosion inhibitors, can form thick,

oily surface films, which may

severely retard heat transfer. This

may lead to an increased demand in

primary energy. In general, organic

inhibitors are described as not

suitable for higher temperatures.

Organic inhibitors are described to be

suitable in alkaline pH. However,

available scientific literature rather

refers to corrosion processes in acidic

media and data is therefore less

assignable to AADC systems

operating in the range of pH 9 to 12.





organic inhibitors. However, its capability


systems is not yet proven. Therefore, a

detailed R&D process including long-

term testing on a pilot scale and further

industrial upscaling have to be performed

before the final performance of organic

inhibitors can be assessed ultimately.

Azole and

azoline

Imidazole is an aromatic heterocycle

which is known as a component of

several biochemical molecules and for

its anti-fungal properties. Imidazole

derivatives are described as

adsorption-type, organic inhibitor that

forms a hydrophobic film on metal

surfaces and hinders the corrosion

reaction by this barrier. Imidazole-

There is evidence that imidazoline

provides an inhibition efficiency of

maximum 90 % at a temperature of

about 150°C at 207 bar (Chen,

2000). This inhibition performance is

considered insufficient for the

application of imidazoline as

corrosion inhibitor in AADC systems

operated by H&R.



73


based corrosion inhibitors, e.g. 1-

methyl 2-mercapto imidazole are

mainly used in crude oil and gas

industry to protect work effectively

against CO2 corrosion (Ahmad Jaal et

al., 2014).

A number of studies discussing

imidazoline derivatives show that

high rates of shear stress, turbulent

flow conditions and bubble impact

significantly decrease the corrosion

inhibition performance of these

substances. Under these conditions

the inhibitor film is destroyed or

removed from the surface (Chen,

2000; Hong et al., 2002; Chen and

Jepson, 1999).

In summary, some key requirements for



chilled water systems may be fulfilled for

some azoles like imidazole. Nevertheless,

literature results indicate that this

corrosion inhibitor might not be effective

in the given temperature range and at the

given turbidity. Additionally, the

capability for the safe and long-term use

in AADC systems is not yet proven.

Therefore, these substances are not

considered as an alternative to sodium

dichromate.



74

Appendix 2 – Information on chemical substances assessed in Section 6.3

Appendix 2.1: Ammonium molybdate

Table 1: Substance IDs and properties for relevant substances:

Parameter Value Physicochemical

properties Value

Chemical name and

composition

Ammonium molybdate

(VI) tetrahydrate

Physical state at 20 °C

and 101.3 kPa Solid (crystalline)

EC number - Melting point 90 °C (dec.)

CAS number 12054-85-2 Density 2.498 g/cm3

IUPAC name Ammonium molybdate

(VI) tetrahydrate Vapour pressure -

Molecular formula (NH4)6Mo7O24 • 4H2O Water solubility 430 g/L (20 °C)

Molecular weight 1235.86 g/mol Flammability

Flash point -

Table 2: Hazard classification and labelling

Substance Name

Hazard

Class and

Category

Code(s)

Hazard Statement

Code(s)

(labelling)

Number

of

Notifiers

Additional

classification

and labelling

comments

Regulatory and

CLP status

Ammonium

molybdate (VI)

(CAS 13106-76-

8)

(EC 236-031-3)

Acute Tox.

4

H302 (Harmful if

swallowed) 82

Number of

notifiers of 17

parties were

summed up.

Not REACH

registered;

Not included in

the CLP

Regulation,

Annex VI;

Included in C&L

inventory

Skin Irrit. 2 H315 (causes skin

irritation) 89

Eye Irrit. 2

H319 (Causes

serious eye

irritation)

89

STOT SE 3 H335 (May cause

resp. irritation) 84

STOT RE 2 H373 (May cause

damage to organs) 1

Aquatic

Chronic 3

H412 (Harmful to

aquatic life with

long lasting effects)

19

Aquatic

Chronic 4

H413 (May cause

long lasting 2



75

Substance Name

Hazard

Class and

Category

Code(s)

Hazard Statement

Code(s)

(labelling)

Number

of

Notifiers

Additional

classification

and labelling

comments

Regulatory and

CLP status

harmful effects to

aquatic life)

Skin Sens.

1

H317 (May cause

an allergic skin

reaction)

4

Resp. Sens.

1

H334 (May cause

allergy or asthma

symptoms or

breathing

difficulties if

inhaled)

4

Muta. 2

H341 (Suspected of

causing genetic

defects)

1

Carc. 2 H351 (Suspected of

causing cancer) 1

Appendix 2.2: Sodium nitrite



properties Value

Chemical name and

composition

Sodium nitrite (mono

constituent substance)


and 101.3 kPa solid

EC number 231-555-9 Melting point 217 °C

CAS number 7632-00-0 Density 2.17 g/cm³

IUPAC name Sodium nitrite Vapour pressure 9.9x10-17 hPa (25 °C)

Molecular formula NO2.Na Water solubility 848 g/L (25 °C)


Flash point Non-flammable



76


Substance Name

Hazard

Class and

Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

Numbe

r of

Notifier

s

Additional

classification and

labelling

comments

Regulatory and

CLP status

Sodium nitrite

(CAS 7632-00-0)

(EC 231-555-9)

Ox. Sol. 3

H272 (May

intensify fire;

oxidiser)

n/a -

REACH registered;

Included in CLP

Regulation, Annex

VI (index number

007-010-00-4)

Acute

Tox. 3

H301 (Toxic if

swallowed)

Aquatic

Acute 1

H400 (Very

toxic to aquatic

life)

Appendix 2.3: Silicate based corrosion inhibitors



properties Value

Chemical name and

composition

Calcium metasilicate (mono


Physical state at 20 °C and

101.3 kPa Solid

EC Number 233-250-6 Melting point 1540 °C

CAS Number 10101-39-0 Density 2.900 g/cm³

IUPAC name Calcium metasilicate Vapour pressure -

Molecular formula CaO3Si Water solubility -

Molecular weight 116.16 g/mol Flammability -


properties Value

Chemical name and

composition

Calcium borosilicate (mono


Physical state at 20 °C and

101.3 kPa

Solid (white

powder)

EC Number - Melting point > 1540 °C

CAS Number 59794-15-9 Density 2.65 g/cm3

IUPAC name Calcium borate silicate Vapour pressure -

Molecular formula 1.4 CaO.0.5 B2O3.SiO2.H2O Water solubility 0.34 g/L




77


Substance

Name

Hazard

Class and

Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

No. of

Notifiers

(CLP

inventory)

Additional

classification and

labelling

comments

Regulatory and

CLP status

Calcium

metasilicate

(CAS

13983-17-0)

(EC 237-

772-5)

Not

classified - 335

For reasons of

simplicity the

numbers of

notifiers were

added if the

reported hazard

classification was

identical.

Currently not

REACH registered;

Not included in CLP

Regulation, Annex

VI;

Eye Irrit. 2

H319 (Causes

serious eye

irritation)

166

STOT SE

3

H335 (May cause

respiratory

irritation)

132

STOT

RE2

H373 (May cause

damage to lungs) 166

Calcium

borosiliate

(CAS

59794-15-9)

- - -

No classification

information

available.

Not REACH

registered;

Not included in CLP

Regulation, Annex

VI;

No CLP

classification

notified;

Appendix 2.4: Zinc based corrosion inhibitors



properties Value

Chemical name and

composition

Zinc (mono constituent

substance)


and 101.3 kPa Solid

EC Number 231-175-3 Melting point 409 °C (Zn powder)

CAS Number 7440-66-6 Density 6.9 g/cm³ (22 °C)

IUPAC name Zinc Vapour pressure -

Molecular formula Zn Water solubility

0.1 mg/L (20 °C, pH =

6.93-8.57, powder

form)

Molecular weight 65.409 g/mol Flammability Non-flammable



78


properties Value

Chemical name and

composition

Zinc phosphate (mono



and 101.3 kPa Solid

EC Number 231-944-3 Melting point 846 °C (1013 hPa)

CAS Number 7779-90-0 Density 3.26 g/cm³ (22 °C)

IUPAC name Trizinc bis(orthophosphate) Vapour pressure -

Molecular formula Zn3(PO4)2 Water solubility 2.7 mg/L (20 °C, pH ≈

7)



Substance

Name

Hazard Class

and Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

No. of

Notifiers

(CLP

inventory)

Additional

classification

and labelling

comments

Regulatory and

CLP status

Zinc

(CAS

7440-66-6)

(EC 231-

175-3)

Pyr. Sol. 1

H250 (Catches

fire

spontaneously

if exposed to

air)

n/a -

REACH registered;

Included in CLP

Regulation, Annex

VI (index number

030-001-00-1)

Water-react. 1

H260 (In

contact with

water releases

flammable

gases which

may ignite

spontaneously)

Aquatic Acute 1

H400 (Very

toxic to

aquatic life)

Aquatic Chronic

1

H410 (Very

toxic to

aquatic life

with long

lasting effects)

Zinc

Phosphate Aquatic Acute 1

H400 (Very

toxic to

aquatic life)

n/a -

REACH registered;

Included in CLP

Regulation, Annex



79

Substance

Name

Hazard Class

and Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

No. of

Notifiers

(CLP

inventory)

Additional

classification

and labelling

comments

Regulatory and

CLP status

(CAS

7779-90-0)

(EC 231-

944-3)

Aquatic Chronic

1

H410 (Very

toxic to

aquatic life

with long

lasting effects)

VI (index number

030-011-00-6);

Included in CoRAP-

list

Appendix 2.5: Strong alkaline solutions



properties Value

Chemical name and

composition Potassium hydroxide


and 101.3 kPa Solid


CAS number 1310-58-3 Density 2.044 g/cm³ (20 °C)

IUPAC name Potassium hydroxide

Caustic potash Vapour pressure -

Molecular formula KOH Water solubility 1210 g/L (25 °C)


Flash point -

CRC Handbook


Substance Name

Hazard Class

and Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

Number

of

Notifiers

Additional

classification

and labelling

comments

Regulatory and

CLP status

Potassium

hydroxide

(CAS 1310-58-3)

(EC 215-181-3)

Acute Tox. 4

H302

(Harmful if

swallowed)

n/a Harmonised

classification

(CLP

Regulation)

REACH

registered;

Included in CLP

Regulation,

Annex VI (index

number 019-

002-00-8)

Skin Corr. 1A

H314 (Causes

severe skin

burns and eye

damage)

n/a



80

Appendix 2.6: Phosphate and phosphonate compounds



properties Value

Chemical name and

composition

Trisodium

orthophosphate

Physical state at 20°C


EC number 231-509-8 Melting point 1583 °C (101 kPa)

CAS number 7601-54-9 Density 2.543 g/cm3 (25 °C)

IUPAC name Trisodium phosphate Vapour pressure -

Molecular formula Na3PO4 Water solubility 145 g/ L (25 °C)


Flash point -

CRC Handbook


Substance Name

Hazard

Class and

Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

Number of

Notifiers

Additional

classificatio

n and

labelling

comments

Regulatory and

CLP status

Trisodium

orthophosphate

(CAS 7601-54-9)

(EC 231-509-8)

Skin Irrit. 2 H315 (causes

skin irritation) 689

25

Notifications

, 1 joint

entry

REACH registered;

Not included in CLP

Regulation, Annex

VI

Eye Irrit. 2

H319 (Causes

serious eye

irritation)

332

STOT SE 3

H335 (May

cause resp.

irritation)

229

Eye Dam. 1

H 318 (Causes

serious eye

damage)

377

Skin Corr.

1B

H 314 (Causes

severe skin

burns and eye

damage)

84

Skin Corr.

1A

H 314 (Causes

severe skin 13



81

Substance Name

Hazard

Class and

Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

Number of

Notifiers

Additional

classificatio

n and

labelling

comments

Regulatory and

CLP status

burns and eye

damage)

Skin Corr.

1C

H 314 (Causes

severe skin

burns and eye

damage)

3

Met. Corr.

1

H 290 (May be

corrosive to

metals)

3

Acute Tox.

3

H 331 (Toxic if

inhaled) 3

Appendix 2.7: Rare earth metal salts



properties Value

Chemical name and

composition Cerium trinitrate




CAS number 10108-73-3 Density 2.4 g/cm³ (20 °C)

IUPAC name Cerium trinitrate Vapour pressure < 8.17 *10-7 Pa (20 °C)

Molecular formula Ce(NO3)3 Water solubility > 600 g/L

Molecular weight 326 g/mol Flammability

Flash point Non flammable



82


Substance Name

Hazard Class

and Category

Code(s)

Hazard

Statement

Code(s)

(labelling)

Number

of

Notifiers

Additional

classification

and labelling

comments

Regulatory and

CLP status

Cerium trinitrate

(CAS 10108-73-

3)

(EC 233-297-2)

Ox. Sol. 3

H272 (May

intensify fire,

oxidizer)

9

141 notifiers,

1 joint entry

REACH

registered; Not

included in CLP

Regulation,

Annex VI

Ox. Sol. 2

H272 (May

intensify fire,

oxidizer)

78

Ox. Sol 1

H271 (May

cause fire or

explosion,

strong oxidizer)

25

Eye Dam. 1

H318 (Causes

serious eye

damage)

83

Aquatic Acute 1

H400 (very

toxic to aquatic

life)

103

Aquatic Chronic

1

H410 (very

toxic to aquatic

life with long

lasting effects)

103

Eye Irrit. 2

H319 (Causes

serious eye

irritation)

57

Skin Irrit. 2 H315 (Causes

skin irritation) 11

STOT SE 3

H335 (May

cause

respiratory

irritation)

Aquatic Chronic

3

H412 (Harmful

to aquatic life

with long

lasting effects)

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