Presentation to NACE Middle East & African Branch

Corrosion Under Fire Protection

- Ian Bradley, International Paint Saudi Arabia Limited (IPSAL)

• Types of passive fireproofing (PFP)• Commonly found corrosion problems• Corrosion testing for PFP systems

– UL exterior listing– Norsok– Comparison

• Guidance for specifying PFP systems in corrosive environments• Summary• 20 – 25 minutes• Questions & Answers session

Contents

Types of passive fire protection

• Dense Concrete

• Lightweight Cementitious

• Solvent based and solvent free Epoxy intumescents

• Subliming materials

• Mineral Wool (and other insulations)

ISO 12944 – C5

• ISO 12944 developed to assist engineers

• Global standard

• Designates environments according corrosivity

• Based upon corrosion of steel < 120ºC

• C5 - M superseded by ISO 20340

• Addresses corrosion aspect but not fire performance

• A typical plant may encompass several environments

– Jetty

– Areas around cooling water towers etc

Some examples of corrosion beneath passive fire protection

Examples of corrosion behind PFP

Corrosion beneath concrete fireproofing – C5 I environment (Southern Europe)

Vessel support structureVessel support structure

Corrosion cycle

Loss of passivation effect

• Acidic industrial atmosphere

• Decrease in pH

• Leads to loss of passivity

• Active corrosion beneath cementitious materials

Examples of corrosion behind PFP

Corrosion beneath concrete fireproofing – C5I environment (Southern Europe)

Note significant thinning of section flange

Examples of corrosion behind PFP

Pitting corrosion behind lightweight cementitious fireproofing C5I

Pitting corrosion caused by ingress of calcium chloride during maintenance on vessel

LPG drier in refineryLPG drier in refinery

Examples of corrosion behind PFP

General corrosion behind delaminated fireproofing material C5 - M

Structural steel offshoreStructural steel offshore

Examples of corrosion behind PFP

Delamination of topcoat and subsequent deteoriation of passive fire protection material C5-M

Structural steel offshoreStructural steel offshore

Examples of corrosion behind PFP

Severe corrosion of structural I sections beneath fireproofing

Chemical Plant USA (C5-I)Chemical Plant USA (C5-I)

Examples of corrosion behind PFP

Gas pipe-work support structure

Structural steel onshore C4 / C5-IStructural steel onshore C4 / C5-I

Examples of corrosion behind PFP

Process vessel and structural steel offshore

Structural steel offshore C5 -MStructural steel offshore C5 -M

Examples of corrosion behind PFP

LPG Sphere Leg

Structural steel onshore C5 - MStructural steel onshore C5 - M

Some contributing factors

• No coating or inadequate coating beneath

• Testing of fire monitors containing water or worse seawater

• Lack of flashing plates / sealing caps

• No stand off

• But no bond to surface either

• Non destructive NDT difficult / impossible

When specifying fire protection materials

What do engineers concentrate on?

• Fire performance• Fire duration• Critical core temperature• Type of fire (hydrocarbon, cellulosic, jet fire)• Cost (Fire protection is a major cost item on new

plant)• Still too little emphasis on durability and

weatherability

For fire protection to be effective it must be present For fire protection to be effective it must be present and intact at the time of the fireand intact at the time of the fire

How do we define intact?

Many ways you could define “intact”

• Unaltered from as built condition• Free from significant amounts of water• Bonded to the substrate• Whole (i.e. free from cracks, corrosion paths etc)• But we need something subjective!!

– i.e. test standard• High impact if wrong decision is made

Early attempts to measure weathering

DiBt

• German standard for fireproofing• Requires non-accelerated weathering samples• Fire tested at regular periods• Cellulosic fire protection (buildings)• Long time periods involvedGASAFE

• LPG fire protection program• 1990’s• Tried to address weathering aspect• Limited success

More Recent Attempts

UL1709

• UL 1709 addresses fire performance• “Exterior listing” addresses weathering• Accelerated weathering• Will then list complete system• Follow up service – compliance with as tested materialNORSOK

• Numerous revisions (covered later)• Designed for offshore (C5-M)• Accelerated weathering• Generic type based• Two categories

UL 1709 Exterior Listing

Test Standard Comments

Aging Circulating oven 70ºC for 170 days

Humidity - 97-100% humidity, 180 days

Industrial atmosphere - 1% SO2 / 1% CO2 in chamber + water. 95F for 30 days

Salt spray ASTM B117 90 days salt fog testing

Wet Freeze Dry Cycling - 0.05 mm/ s water for 72 hours,-40ºC for 24 hours,60ºC for 24 hours repeated for 12 repeated for 12 cyclescycles

Fire testing UL 1709 Must meet original acceptance criteria

Norsok M501 Revision 5

Test Standard Comments

Ageing resistance ISO 20340 See below

Salt Spray ASTM B117 Artificial seawater, 35ºC, 72 hours

Low temperature -20ºC 24 hours

UVA/Condensation ASTM G53 UVA exposure followed by 100% condensation

Adhesion ISO 4624 Adhesion < 50% reduction from, > original > 3MPa

Scribe Creep - < 3mm

168 hours168 hours

ΣΣ 4200 hrs4200 hrs

Norsok M501 Revision 5 - continued

Test Standard Comments

Blistering, rusting cracking,

ISO 4628 Rating 0 for all

Water absorption - Shall be reported

Fire testing - Fire testing to 400ºC critical core temperature for 60 minutes within 10% or original unexposed test

Norsok M-501 Revision 5 versus Revision 4

• Salt spray and freeze/dry is now a combined cycle• Revision 4

– Salt spray/drying (ISO 7253) + UV-A (G-53) 4200 hours4200 hours– Water / freezing / drying / humidity ISO 2812-2 4200 hours4200 hours

• Evaluation of scribe creep has changed• Tested without top-coats

Corrosion Issues with major generic types

Dense concreteDense concrete

• Prone to damage

• No bond to substrate (undercutting)

• Can retain significant amounts of water (spalling)

• Passivation lost with time in marine / industrial environments

• Needs weather cap / sealing

Lightweight cementitiousLightweight cementitious

• Prone to damage

• No bond to substrate (undercutting)

• Application must be correct

• Similar to dense concrete

• Needs Weather cap / sealing

Corrosion Issues with major generic types

Mineral Fibre / CladdingMineral Fibre / Cladding• Prone to damage• Very absorbent once cladding damaged• Salts in mineral wool may contribute• Needs weather cap / sealing

Epoxy Epoxy • Offer many performance advantages, however,• Generally fire performance / weatherability is a balance• Number of materials where balance is incorrect• More sensitive to application• Careful (and detailed) specification is necessary

Some general trends

• Cement based and mineral fibre systems no longer used in C5-M

• Cannot exclude problems in C5-I• More awareness of extent of C5-M environment

– Jetties– Coastal Refineries + other locations

• Awareness of these corrosion issues• Not translated into action in many parts of industry• Corrosivity of project location remains un-established

(Quantitatively)

Guidance for specifying PFP performance

• Be aware of the problem

• Know your environment

• Question existing practises– Materials– Construction details

• Consider key areas and potential for upgrade

• Consider suitable weatherability criteria

– UL / Norsok

• In conjunction with fire performance

These are safety critical decisionsThese are safety critical decisions

Demonstrated performance by case history

• Applied in 1976

• Inspected and analysed

• BAM - 1992

• No chemical changes in material detected

• Intumescent chemicals unaffected

• C5-M Refinery (The Netherlands)

Conclusions

• Corrosion behind some types of passive fire protection is a real risk

• Durability is as important as initial fire performance• Test procedures exist which can distinguish materials

performance• Recognised and workable standards• Available to use

Questions

Ian.Bradley@AkzoNobel.com