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# 9 November 2015

The beauty of rust

CORROSION NEWS # 9 | 20152

”EARTH, WATER, FIRE, AIR, corrosion happens everywhere!” – this was the motto of the Eurocorr 2015 conference. The conference was a great success with participation of more than 800 participants from over 50 nations. Swerea KIMAB was represented with scientists from our laboratories in Sweden and France and with expertise in all “environments of corrosion” as well as materials selection, design and methods for avoiding corrosion problems. Together with the Royal Institute of Technology, (KTH), in Stockholm we organized the graduate course in corrosion science, which was held on three consecutive days in connection with Eurocorr. This course has now turned into a permanent ingredient and illustrates the successful cooperation between academia and applied research and provides students with the fundamental scientific principles of corrosion as well as their application to industrial problems.

OUR MISSION to turn scientific work into industrial use is reflected in the current issue of Corrosion News, ranging from structural considerations of bridges to aesthetic concerns of modern buildings. Another trend is the increased complexity of the already complicated corrosion mechanisms resulting from more and more advanced surface treatments and the use of multimaterials. An example you can read about is the recently started European project MicroCorr “Improving steel product durability through alloy coating microstructure” where the inextricably intertwined effects of environment and material properties are to be investigated. You can also find information about a new publication as well as certification courses in the area of polymeric welding, where our solid knowledge of traditional welding techniques has been coupled with our competence in polymeric materials. In a previous issue of Corrosion News you could read about “Carbonfibrereinforced polymers in road environments” where not only the metal but also the composite is influenced by the galvanic coupling in such designs.

OUR CUSTOMERS are always in focus and this is especially true for our member companies. On Swerea’s recently launched and integrated web page (www.swerea.se/en/kimab) you can read about Swerea KIMAB members’ day November 18, 2015 where a number of parallel Member Research Consortia (MRC) meetings will be held at Swerea KIMAB’s premises. There are a number of benefits from being a member of an MRC including, but not limited to, access to all proceedings from Eurocorr (2004) and a reduction in the Eurocorr registration fee.

I SUGGEST that you find a relaxing environment where you can read this 9th issue of Corrosion News without the constant interruptions of emails and meetings. Should you find any article of particular interest please feel free to contact us for more information.

Johan TidbladManager, Corrosion Protection & Surface Technology

editorial

CORROSION NEWS # 9 | 2015 3

Editors: Tomas Hult, [email protected] Margaretha Sönnergaard, [email protected]

Advisory Board: Eva Johansson, Eva Lindh Ulmgren,Johan Tidblad, Dominique Thierry.

Printing: EO GrafiskaCover: The new School of Architecture in Stockholm

Corrosion News is published by: Swerea KIMAB, Sweden and Institut de la Corrosion, France

Subscriptions: Swerea KIMAB Corrosion News PO-Box 7047SE-164 07 Kista, Sweden [email protected] www.swereakimab.se

Corrosion News All rights reserved. No part of this publication may be reproduced in any form by any electronic or mechanical means without permission in writing from Swerea KIMAB.

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# 9 2015

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16The concept developed by Andra for underground repositories in-volves the confinement of wastes in clay layers.

In early spring 2015 it became apparent that the the sheetpiling at the Sundsvall Bridge was rusting at a faster rate than expected.

We have learned that rust should be prevented at all costs; but who can resist the warm glow of a rusty façade in the sunlight?

Improving steel product durability through alloy coating microstructure 4

The advantage of determining the dewpoint temperature in flue gas channels 6

Unique exposure study of steel piles in soils 9

Underground repository of high activity long term nuclear wastes 10

The beauty of rust 12

Hello there Bertil Sandberg 15

Sundsvall Bridge protected against corrosive attack 16

Filiform corrosion on aluminium 18

New equipment at Swerea KIMAB 21

Swerea KIMAB has developed a dewpoint meter that has been success-fully used in five projects.


IN ORDER TO INCREASE further the corrosion durability of zinc coated steel products and reduce production and operating costs, steel makers invest a lot into the coating optimization by alloying. Successful examples of coating development are materials alloyed with nickel, chromium, iron and particularly those with aluminium, e.g. Zn5Al and Zn55Al. The present development activity is focused on ZnAlMg and ZnMg coatings for building and automotive applications fabricated by either more traditional hot dipping or physical vapour deposition (PVD) technologies. Several ZnAlMg coated materials of European steelmakers are available now and their market share is growing rapidly due to their superior corrosion and other functional properties: EcoProtect (Zn1Al1Mg) of ThyssenKrupp, MagiZinc (Zn1.6Al1.6Mg) of Tata Steel, Stroncoat (Zn1.6Al1.6Mg) of Salzgitter, Corrender (Zn2Al2Mg) of voestalpine and Magnelis (Zn3.7Al3Mg) of ArcelorMittal. Other ZnAlMg(X) coatings are produced by Asian steel makers.

DUE TO RESEARCH ACTIVITIES of several groups including those from Swerea KIMAB and Institut de la Corrosion, a

Maizières Research, OCAS, Universtity of Chemistry and Technology in Prague and Institut de Recherche de Chimie Paris, with a long track record in corrosion science and protection mechanism of ZnAlMg coatings, are involved. MicroCorr is planned to proceed until February 2019. It is sponsored by Research Fund for Coal and Steel.

THE PRINCIPAL GOAL of MicroCorr is to clarify the relationship between the metallic coating microstructure and corrosion behaviour. It is believed that the size of local galvanic cells strongly affects corrosion processes on alloy coatings and therefore the longterm corrosion performance of coated steel products. Deeper understanding into interactions between coating components as a function of surface pH, contamination and phase size will be acquired in a series of experiments using a number of innovative, mostly insitu, electrochemical, corrosion and surface analytical techniques. A numerical model will be developed allowing coating developers to reduce the time to market for new coated products with superior longterm corrosion stability.

Contact: [email protected]

consensus on the role of principal alloying elements in initial phases of corrosion as well as longterm protection is mostly established. However, very limited attention has been paid to the effect of the coating microstructure on corrosion up to now. Based on analogy to e.g. aluminium and magnesium alloys, it is expected that the microstructure of zinc alloy coatings strongly affects their corrosion properties as well. This aspect is so far widely neglected in zinc alloy design.

TO PROVIDE STEEL MAKERS with the tools to enable the development of new zincbased and zincfree coating materials with superior longterm corrosion stability, a European project “Improving steel product durability through alloy coating microstructure” (with the acronym MicroCorr) has been initiated in September 2015. Institut de la Corrosion serves as a coordinator in the project. Three principal steel producers involved in development of advanced zincbased coatings are participating in the project: ArcelorMittal, Tata Steel and voestalpine. To complete the consortium, research teams from Swerea KIMAB, Max Planck Institut für Eisenforschung, Swansea University, ArcelorMittal

Zinc based coatings are widely used for corrosion protec-tion of steel structures and products in almost all types of environments and applications. The primary task of zinc coatings is to offer cathodic protection to steel. Zinc is a very effective element in this respect as it keeps a delicate balance between sacrificial protection of steel and good long-term stability.

Improving steel product durabilitythrough alloy coating microstructure

BY TOMAS PROSEK & DOMINIQUE THIERRY


Improving steel product durabilitythrough alloy coating microstructure


The advantage of determining the dewpoint temperature in flue gas channels


If the temperature of surfaces in combustion plants is below the so-called dewpoint temperature (TDP) for the flue gas, a very aggressive condensate, which results in extensive corrosion, precipitates on these surfaces.

This condition causes many problems in combustion plants. Among other things, these plants depend on heat exchangers fitted with socalled economizers and air preheaters that utilize recovered flue gases in order to save energy. To avoid precipitation of aggressive condensate on surfaces, the medium entering the heat exchangers is preheated using steam or electricity to maintain a temperature on the surfaces that is above TDP. However, it is only possible to have a rough estimate of TDP, so this preheating is done with a good safety margin. If TDP could be predicted with greater accuracy, it may be possible to reduce the temperature of the input medium without the risk of condensate precipitating on surfaces, and thereby avoid corrosion damage and the risk of the plant having to be shut down. A reduction in temperature of just a few degrees would improve plant performance dramatically. In addition, this presents good conditions for reducing energy losses.

Another problem is associated with the plant’s superheaters, heat exchangers that superheat steam that goes to the plant’s turbines. These superheaters are often subject to extensive corrosion, which is largely a result of salt deposits forming on the tube surfaces. One way of preventing this is to add some form of sulphur to the fuel in the combustion chamber. However, this increases the sulphur content in the flue gas, which in turn raises the TDP for the flue gas. If the level to which the TDP is raised as a result of sulphur addition is not known, there is a risk of surfaces exposed to the flue gas, after the superheaters, being subjected to extensive corrosion. If, due to the fear of this happening, no sulphur addition is made, the problem of corrosion on the superheater surfaces remains.

Finally, a problem associated with increased TDP is that there may be a change in fuel composition, either intentionally e.g., through the use of cheap fuel or, unintentionally, due to deviations in the fuel composition promised by the fuel supplier. If the value of the resulting TDP is not known, there is a risk that the TDP may rise above an acceptable level and remain there for a prolonged period, thereby resulting in condensation and, consequently, corrosion damage.

Prediction methods for dewpoints The condensate temperature can be estimated theoretically. For oilfired plants, there are equations that can be used to predict dewpoint temperature with certain known fluegas compositions. However, for coalfired, biofuelfired or WTE (wastetoenergy) power plants the flue gas is more complex, and using existing theoretical equations for these is considered highly unreliable. Even more uncertain is prediction of dewpoint temperature in the presence of hygroscopic salts i.e., salts that absorb moisture.

Swerea KIMAB has developed a dewpoint meter (see Figures 1–3) that has been successfully used and developed in five projects funded by Jernkontoret, ECSC, KME, Värmeforsk and Ångpanneföreningen’s research foundation. It was also used in a project commissioned in 2014 by Sysav’s WTE plant to assess conditions for reducing the temperature in their economizer.

The only commercially available dewpoint meter is provided by Land Instrument International. A comparative test with Swerea KIMAB’s dewpoint meter and Land’s dewpoint meter was done at one of Götaverken Miljö’s plants in 2009. Here, Swerea KIMAB’s dewpoint meter indicated an increased

Fig 1. Swerea KIMAB’s dewpoint meter, approx. 2 m long.


dewpoint when sulphur was added, while Land’s dewpoint meter showed no appreciable difference. Land’s dewpoint meter was also used in 2014 in a Värmeforsk project to measure dewpoint temperature in the flue of a recovery boiler, but no acid dewpoint was detected.

Another probe instrument for detecting corrosion and acid deposition, developed by Vattenfall, can give an indication of dewpoint temperature. However, a disadvantage with this probe is that it may require an exposure time of several months under relatively constant conditions.

Development work There are several aspects of Swerea KIMAB’s dewpoint meter that still require development. Swerea KIMAB’s dewpoint meter has limited cooling capacity, which means that the obtained TDP is relatively inaccurate if the flue gas temperature is high, which may be the case with flue gas upstream of the economizer. Also, the dewpoint meter is relatively difficult to handle, and it requires Swerea KIMAB’s personnel to be present during the measurement period, which means the cost of measurement can be relatively high. Finally, in WTE plants the TDP can fluctuate widely during certain periods, depending on the composition of the fuel. This means that there is a risk that these higher TDP values may not arise during the measurement period during which the dewpoint meter is used.

Swerea KIMAB is now working to remedy these deficiencies. A more user friendly and welldocumented functional version of Swerea KIMAB’s dewpoint meter, as well as a more wellestablished relationship between flue gas composition and dewpoint temperature, would be of interest not only from an academic perspective, but also from an industryrelevant perspective.


R T

• • •

Construction Above left is the sensor plate with two concentric metallic spirals, electrically isolated and con-nected to a resistivity meter (R). Above right is a principle drawing of the dew point meter, inserted into a flue gas channel. The sensor plate (orange) with its spirals (red) is cooled by compressed air (black arrows), and the temperature of the sensor plate is measured by a temperature probe con-nected to a temperature meter (T).

Measuring procedureInitially the temperature of the sensor plate has a temperature equal to the temperature of the flue gas. When the cooling starts the temperature of the sensor plate is gradually lowered, and when the temperature of the sensor plate reaches the dew point temperature of the flue gas, a conden-sate forms on the sensor plate. Then the metallic spirals will be in electrical contact with each other which results in a signal on the resistivity meter. The temperature value is read, and the value is interpreted as the dew point temperature.

Fig 2. Sensor surface and principle drawing

R T

Fig 3. Measurement in exhaust gas channel with Swerea KIMAB’s dewpoint meter.

Flue


CORROSION IN SOILS is very complex, since so many variables are involved. The most decisive factors are oxygen transport and moisture content. Other factors which may have an impact are groundwater level, soil type, resistivity, organic matter content, pH and the presence of contaminants such as coke. To further complicate the matter, these soil parameters can vary in both the vertical and horizontal directions.

In a study in which steel pilings have been exposed for 33 years it can be clearly seen that corrosion attacks vary widely in different soils and on different areas of each individual piling. This agrees well with the results from earlier test samples that have been removed regularly since the early 1980’s. Swerea KIMAB (at that time, the Swedish Corrosion Institute) initiated an exposure study in various soils in different locations throughout Sweden to determine how corrosivity varied. Since then, samples have been removed for examination after 5, 9, 20 and 27 years of exposure.

Much critical infrastructure is buried in soil and is, as such, exposed to the corrosivity of the soil. This infrastructure may include water and sewage mains, abutments, culverts and steel pilings. In Sweden, during 2013 more than 1.8 million meters of pilings were used in construction. Of these, about 710,000 were steel pilings. These are buried or driven into the ground to provide stability for different types of structures, such as buildings and roads. According to the longterm study that we have conducted, the corrosivity to which these are exposed can result in major problems. To prevent these problems it is therefore important to be able to predict the corrosivity that is specific to each location.

In the thesis project “Corrosion of steel pilings after longterm exposure in soil” by Jonas Engblom it was found that the average rate of corrosion can

be classified into two groups. One group includes two sandy soils and clay, and the other group comprises three soils currently classified as gytja clay i.e., clays containing a high content of organic material. For the first group the latest measurement showed a corrosion rate of about two to three μm/yr and the latter between six and eight μm/yr. This classification has also been observed in the earlier measurements.

There were indications that water content and pH might have an effect on the rate of corrosion, but neither resistivity nor chloride content seemed to have a marked effect on the average rate of corrosion.

Pitting formation A marked difference in the occurrence of pitting was also observed. Pitting formation has been most clearly seen in the locations where the pilings have been exposed to dry, sandy soil.

Pilings exposed below the groundwater table or in very moist soil showed very little or no pitting.

Corrosion rates also varied between areas on one and the same pole. In three locations with gytja clay an increase in the rate of corrosion was noted at a depth of about one metre; in one case the increase was as much as 16 μm/yr. This increase occurred at a depth just

below the groundwater table. In two of the other locations with gytja clay the increase, although apparent, was not as pronounced, and was noted just over a metre below the groundwater table. Although pilings that were exposed to clay showed certain signs of an increase in the rate of corrosion at a depth of about one metre, this was not as evident as it was in pilings exposed to gytja clays. Pilings that were removed from the two test locations with sandy soils had not breached the groundwater table, or had only done so during what in this context may be considered a very limited period.

Contact [email protected]

Unique exposure study of steel piles in soils

Sections of different pilings taken from the same depth. From left: gytja clay; drained, sandy soil and clay.

Removal of a steel piling after 33 years of exposure in clay, Enköping.


THE CONCEPT DEVELOPED by Andra* for underground repositories involves the confinement of wastes in clay layers. A steel casing is introduced in a micro tunnel drilled in the clay layer, in which overpacks are emplaced (figure 1).

The carbon steels considered for both casing and overpacks will be in contact with clay and/or with seepage water in equilibrium with clay, first in solutions containing dissolved oxygen, then in anoxic conditions. A maximum temperature of 90 °C is expected after the introduction of overpacks. The pH of the solutions varies from slightly acidic to slightly alkaline, and dissolved gases are present (CO2, H2 formed by the cathodic reaction of the corrosion processes). The chemical composition is complex, with the presence of carbonates, silicates, sulphates…[1].

Failures induced by Stress Corrosion Cracking (SCC) have been reported for pipes buried in soils, in specific conditions, a problem which has been extensively studied by the Oil and Gas

industry. Two domains of possible SCC were identified [2], corresponding respectively to conditions leading to:– high potentials (aerated environ

ments) with high carbonate contents (intergranular cracking),

– low potentials (anoxic conditions) (transgranular cracking in near neutral solutions).

This last process seems to require dynamic loading to become significant and is favoured by steel microstructural heterogeneities. Synergistic effect between anodic dissolution and local hydrogen embrittlement accounts for the cracking mechanism.

Even if the repository conditions do not correspond to those described above to trigger SCC and could be considered as not critical with respect to Environmental Assisted Cracking (EAC), the requirement for extended lifetimes of the overpacks and casing implies an analysis of the potential occurrence of EAC. Optimized microstructures with respect to near neutral

SCC and hydrogen embrittlement have also been considered for material selection and these requirements have been included in the material specifications.

A program dedicated to the evaluation of SCC sensitivity of carbon steels selected for casing and overpacks was launched by Andra several years ago. Institut de la Corrosion is has been one of the main contributors to this program since 2008.

THE MAIN TASKS of Institut de la Corrosion were to address the material behaviour in both initiation and propagation stages. Testing facilities were developed to perform long term SCC experiments (up to 8000 hours) with stressed specimens in clay environments. Specimens were either buried in clay mud or positioned in the solution on top of the mud. Specific spring loading frames (figure 2) were used for tensile specimens and compact tensile precracked specimens. They were immersed in large cells, heated at 90 °C, in which a

Underground repository of high activity long term nuclear waste– Environmental assisted cracking of casing and steel overpacks

BY CLAUDE DURET THUAL


Clay mud, sampled from the repository location

View of speci-mens located in the solution on top of the mud

specific gas mixture was continuously bubbled (figure 3). Additional specimens were introduced for continuous free corrosion potential monitoring, as well as, corrosion rate measurements. The pH evolution of the solution was also continuously followedmonitored.

Several testing campaigns have been performed, on different materials, including welds, to help in with the material selection process.

EFFECTS RELATED TO cold work were evidenced on tensile specimens tested as machined, with the formation of microcracks at the material surface (figure 4). The occurrence of microcracking has also been reported in the two SCC modes (high potential and low potential) described for buried pipelines and in other SCC systems. Considering the propagation stage, the propagation of a single long crack hinders the intermediate process of growth and coalescence of microcracks, which is a significant part of the cracking process, thus affecting lifetime prediction. To study this specific problem, Andra and Institut de la Corrosion participated to in an ANR** research project named ECCOFIC, dedicated to the study of the coalescence of microcrack colonies (project leader INSA*** Lyon, project started in 2014).

Andra recently strengthened its relationship with Institut de la Corrosion via a collaboration contract and by supporting a research work (thesis) conducted both at INSA Lyon and “Institut de la Corrosion” by Nicolas Bulidon, member of the St Etienne team and in charge of the Andra SCC evaluation program. Due to the evolution and improvement of the repository concept, new experiments are being developpeddeveloped.


Figure 1: View of the micro tunnel with the steel overpacks.

Figure 2: Stressing frame with the CT specimen.

Figure 3: Heated test cell, 80 liters capacity.

Figure 4: SEM image of a tensile specimen surface after 8000 hours testing in clay (as machined condition) – microcracks induced by cold working.

*Agence Nationale pour la gestion des Déchets Radioactifs**Agence Nationale de la Recherche***Institut National des Sciences Appliquées [1] J.M.Gras et al. – Journées Andra GL-VFA Paris 17–18 juin 2013[2] P. Combrade et al. - Journées Andra GL-VFA Paris 17–18 juin 2013


We have learned that rust should be prevented at all costs; but who can resist the warm glow of a rusty façade in the sunlight?

Oh no, a rust spot! We have learned to think of rust as a negative occurrence. Even so, one architectural firm after another insists on choosing rust as a sustainable and maintenancefree façade alternative. We recently had a chance to see renditions of a new housing project in Skellefteå by the architects at Tema. Weathering steel will grace the

façades of buildings in the residential area of Heimdall,where housing company Skebo is the client.

– We have chosen weathering steel for several reasons. One is that the client, the municipal housing company Skebo, wanted a good material. Another is that we were looking for a material that has a distinctive character, like materials

such as stucco, brick and wood. Two of the three buildings will be constructed in the courtyard and one on the outskirts of an existing residential quarter. The new buildings will have great significance. Rusty façades will be attractive against the surrounding greenery. Sustainability is another aspect, and the material is also fire resistant, says Björn Odéen, managing architect at Tema.

Weathering steel is commonly referred to as Corten steel (Corten is a registered US trademark). This steel alloy has primarily been used in heating boilers, plate steel wood stoves and chimneys, since it withstands high temperatures and retains its shape. Another

The beauty of rust

TEXT CECILIA ÖFVERHOLM


advantage of weathering steel is that it can be produced in thin dimensions.

– It is a living material that changes all the time. Old sheets turn a dark, blackish brown and sometimes must be replaced, explains Björn Odéen.

School of Architecture.Rust also seems to match well aesthetically with other materials. This is one reason why architectural firm Tham & Videgård chose weathering steel for the façade of the new KTH School of Architecture.

– It’s a matter of context; how the new school looks in relation to the surrounding, older, more traditionally

constructed buildings. Weathering steel matches the same colour scale as the dark, handmade brick and, over time, acquires a patina that can marry well with the feel and material presence of the brick. This is a way of using contemporary industrial building processes to achieve the appearance of a crafted material, says Bolle Tham.

In Sundbyberg, outside Stockholm, the architectural firm Brunnberg & Forshed’s Signalfabriken project was given a rusty façade for aesthetic reasons. Here, buildings that once housed nineteenthcentury industries have been remodelled to make way for dwellings, business premises and restaurants. Among other things, Brunnberg & Forshed designed one of the entrance buildings for the new residential quarter.

– It was to have a distinctive character and was therefore given a façade of weathering steel. The building features a portico that opens onto a square, and opposite is a former telephone exchange in reddishbrown brick that we weren’t allowed to touch, says Andreas Svensson of Brunnberg & Forshed.

The quarter is a melange of function

alist and findesiècle styles, brick and stucco. It forms a complete ensemble, a variegated family of buildings into which the rusty façade blends well.

– The façade is clad in a material that also echoes the industrial history of the place, adds Andreas Svensson.

The quarter was once called Plåten (‘the plate’), but that is merely a matter of curiosity. An earlier example by Brunnberg & Forshed has been deemed the first Nordic multifamily dwelling with a rusty façade, although that may not be entirely true. However, these buildings do merit plenty of attention. On Främlingsvägen, just outside Stockholm’s urban centre, a cluster of redbrick apartment blocks, home to many young families, has stood in solitary majesty upon a hill since the 1940’s. When the quarter was to be densified Stockholmshem hired the firm to draw new and modern multifamily dwellings that would preserve the character and cultural heritage values of the area. Therefore, there was a strong incentive to create something that would blend in like a chameleon. Weathering steel was chosen for the façades. An added

JOHAN TIDBLAD, senior researcher at Swerea KIMAB on the composition: – The material is carbon steel with minor amounts of copper, phosphorus, silica, chromium and nickel (from about 0.1 percent to about 1 percent).

Why the material rusts– When steel is made from iron ore, energy is added. Corrosion is a natural process that, in principle, causes iron to revert to ore. Therefore; corrosion cannot be stopped, only inhibited. Rust, which also forms on weathering steel, contains ferric oxyhydroxide.

– The corrosion process continues, but at a slow rate. In Sweden, it is about the same rate as that of common steel. For most materials, corrosion

rate declines over time, since corrosion results in corrosion products. Depending on material and environment, different types of corrosion products, which can be more or less protective, form – the more protective, the slower the rate, says Johan Tidblad.

Appearance and design– Weathering steel is also known as Corten steel. For the steel to acquire the desired appearance, design is impor-tant. Atmospheric conditions must shift between wet and dry. The appearence of the material isn’t as attractive if it is pro-tected from the rain or in areas that are more or less always wet, nor do façades last as long in such areas. Design is therefore vital, concludes Johan Tidblad.

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advantage is that weathering steel is cheaper than brick and just as maintenancefree.

Hesitant about rustInitially, Stockholmshem was hesitant about rust, since they felt it might stain residents’ and visitors’ clothing.

– The rust precipitates during the first years, but when I visited Främlingsvägen after about six months, it had already stopped, says Rikard Hedin of Brunnberg & Forshed.

However, Stockholmshem’s hesitancy was not unfounded. Johan Tidblad is a senior researcher and manager at Swerea KIMAB (formerly the Swedish Corrosion Institute). When asked if he would choose weathering steel as façade cladding on his own home, he replies:

– No. I don’t think so. The reason is that you would want to avoid direct contact, since the surface could leave rust stains on my clothes and the rest of the family’s. Therefore, I would only recommend weathering steel for surfaces that are not easily accessed, or for sculptures that are not meant to be touched.

Even so, there is something enchanting about the warm glow of sunlight on a rusty steel façade.

Contact: [email protected] KTH School of Architecture in Stockholm.

A one-day seminar organized by TWI and Swerea KIMAB where the results from the European Project RFCS JOINOX will be presented. It will deal with the relationship between welded joints oxides, corro-sion resistance of welded joints and post-weld cleaning strategies.

Organizing committeeSwerea KIMAB, Voestalpine, TWI Limited, Fundació CTM Centre Tecnològic, Outokumpu Stainless, Sandvik Materials Technology andMax Planck Institut fuer Eisenforschung.

The conference is free of chargeInformation and registration: http://www.twi-global.com/news-events/

Invitation to one-day Dissemination ConferenceGuidelines for use of welded stainless steel in corrosive environments26th January 2016, at TWI Granta Park (Cambridge, UK)


Hello there...

...Bertil Sandberg, A veteran corrosion special-ist at Swerea KIMAB over the years, you have worked on hundreds of different corrosion-related assign-ments.

What is it that still attracts you? – No task is like another. You face new challenges every time. And the work has a positive impact. You help the client to solve acute problems, a bit like a doctor. And you see rapid results. Besides, I get to learn about a lot of industries and sectors, such as power and energy, infrastructure and the like.

How did you get interested in corro-sion? – I did an engineering MSc in mining and metallurgy and did my thesis project at the Institute for Metals Research, which was at that time located near the Roslagsbanan railway line in Stockholm. When I finished my degree and was looking for a job I applied there first, but there were no vacancies. Anyway, what was then the Swedish Corrosion Institute was in the same building, so I went there and asked – and they hired me. That was nearly 35 years ago.

What kind of assignments have you worked with? – Oh, all kinds. Consultancy work, when I get to work with tangible problemsolving, is probably the most fun. But I have also worked with studies of, for example, cathodic protection and leakage current. I have also worked in most positions in the field, from researcher to president of the former Swedish Corrosion Institute, so you could say I’ve covered the whole spectrum. Clients have often included large

companies such as Vattenfall, ABB, the Swedish Transport Administration and many others. I have also done a lot of offshore work, for example, dealing with corrosion problems with ships. Seawater, of course, is often the culprit.

What are the challenges in your job? – First and foremost, thinking creatively in order to find possible causes and solutions. Also, many assignments are confidential. That things corrode is seldom something you want to broadcast… If, for example, an automaker has a problem with a new model, they don’t want information to leak out in advance, since it might involve a recall. A particularly interesting incident occurred in 2010 in Namibia. The country had for many years imported electricity from South Africa, but a sudden crisis put an end to deliveries. Namibia was forced to seek alternative sources of supply. Transmission lines had to be built to Zambia and Zimbabwe, who were willing to supply power. The simplest solution was a highvoltage directcurrent (HVDC) transmission line. A monopolar system is configured with earth return. The problem was that they ignored the fact that the ground in the Kalahari Desert is extremely dry and, therefore, unsuitable for earthing. However, there were large graphite deposits that could be used for transmission of return current.

Have you ever been surprised? – Oh, many times. I was invited to the Höga Kusten Bridge to carry out an inspection. Once there, I immediately became suspicious when I was treated to coffee and cake; such affairs aren’t usually that fancy. When I put on a safety harness and went up the 182metre pylon, I realized I was in for a very different assignment – my job was to inspect the suspension cables.



In early spring 2015 it became apparent that the Sundsvall Bridge was exposed to corrosive attack, which meant that the sheetpiling on the bridge abutments was rusting at a faster rate than expected. Now, Trafikverket, the Swedish Transport Administration, is conducting a series of tests and diving inspections in Sundsvall Bay to determine the right corrective measures.

Construction of the Sundsvall Bridge began about four years ago. The bridge, part of the E4, is 2109 metres long. It was built across the bay to facilitate travel between the north and south of the city of Sundsvall. Previously, motorists were forced to drive through the city, which added 2.3 kilometres to their journey. The bridge, which was opened to traffic in late 2014, was initially crossed by an average of 13,000 vehicles per day. Several months later, Trafikverket discovered that the rate of corrosion on the sheetpiling for the abutments was much faster than expected. Based on this, it was concluded that, although the corrosion posed no imminent risk, the bridge would not last 120 years as planned.

– Right now, I am studying methods of preventing continued corrosion, explains Bertil Sandberg from Swerea KIMAB. There are several possible methods of protecting the sheetpiling, one of which involves casting in concrete and coating with rustproofing. In addition, we are conducting onsite experiments to study two other possible methods.

One of these is cathodic protection, whereby the potential of the structure to be protected is lowered by feeding current from anodes placed outside the sheetpiling. A range of factors

Sundsvall Bridge protected against corrosive attack

affect the design, such as the salinity of the water, temperature and water currents. Furthermore, the level of protection that is required in the presence of the bacteria that appear to be hastening the progression of natural corrosion has to be verified.

The other is a new method which has not yet been tested and has been developed specifically for a case like the Sundsvall Bridge. Here, a large cap of metallic or polymeric material is used to encapsulate the abutment like a shell and is then sealed. Initially, corrosion will persist, since oxygen and sulphate are present in the water that has been shut in; however, in theory, since no new water can enter, these will diminish and the corrosion will eventually cease. It may even be necessary to place sacrificial anodes inside the cap, since it is difficult to guarantee that it can be fully sealed.

On the whole, Bertil Sandberg is pleased with the trials and optimistic about the future. The trials will continue and based on the tests and studies that have been conducted, the expert group that is linked to the project will select one or more methods and the work will be contracted.



Sundsvall Bridge protected against corrosive attack


MORE AND MORE LIGHTWEIGHT materials are now being used in the automotive industry. A natural tendency is to switch from steel to aluminium. As with most transitions, this entails new problems. When, for example, a steel engine hood is replaced with an aluminium component, a defect or mechanical scratch in the coating can cause flaking or blisters to form under the coating. This type of corrosion, filiform corrosion, only occurs on coated materials and is a common problem seen on aluminium components. To be able to simulate this corrosion and prevent related problems in the future, a new type of corrosion initiation must be developed for laboratory tests in order to produce results that closely resemble those of actual exposure in the field.

IN THIS THESIS PROJECT, three initiation methods have been tested. Three different initiation solutions have been used: aluminium chloride (AlCl3),

hydrochloric acid (HCl) and a saturated solution of aluminium chloride and sodium hydroxide (Al(OH)3 + NaOH). For the first method, a syringe without a needle was used to apply the initiation solution in a scratch in the surface coating of all test samples. The samples were then placed in a climate chamber for six weeks to see whether filiform corrosion would occur. For the second method, a thin dishcloth was used to keep the test sample damp for a longer period. Finally, for the third method, a dishcloth was also used, but the initiation was done in a climate chamber to maintain suitable levels of temperature and humidity. To follow the development of filiform corrosion, photographs were taken every week during the sixweeklong test period. All test samples were inspected visually and under a microscope. All filiform filaments (threadlike forms of corrosion that occur under the coating) on the test samples that were considered most interesting were

Filiform corrosion on aluminium

counted and measured, and the coating that was loose and deteriorated was removed in order to measure the area of the corrosion.

THE RESULTS revealed that the method used to apply the solution makes a greater difference than the solution used, provided that the solution can corrode aluminium. The results also showed that aluminium chloride was the most suitable solution for corroding aluminium. This was evidenced by the fact that aluminium chloride produced filaments that most closely resembled those occurring in field tests and that this solution resulted in a suitable number of filaments.

SOME OF THE PRODUCTS that formed in the corrosion of aluminium were identified and the possible effect that the initiation solutions can have on the different coatings was studied by means of FTIR and SEM with EDS. The coat


1st International Seminar on

Coatings for Corrosion Protection

in Marine & InfrastructureNovember 19, 2015 Stockholm, Sweden

The seminar is divided into three sessions: • Field studies and practical

experiences• Corrosion tests for paint

systems• Evaluation methods and

analytical techniques

Info & registration www.swereakimab.se

ings that were tested were not affected by any of the initiation solutions. FTIR showed that the same product (aluminium hydroxide gel) formed in all filaments, regardless of the type of initiation solution used. FTIR also showed that the scratches on each test sample contained a mixture of the corrosion product arising in the filaments and the product that results from corrosion of aluminium without coating for each solution.

OUR RECOMMENDATION is that further studies on this subject should be done and that the third initiation method should be used in combination with aluminium chloride as initiator. One

FACTS

The object of this thesis project has been to develop an corrosion initiation process that can be used on painted and/or coated aluminium alloys as a complement to existing accelerated corrosion testing that is used on steel.

factor that should be studied in greater detail is how long the test sample should be exposed to the initiation solution before the dishcloth is removed.


A thin dishcloth was used to keep the test sample damp for a longer period.

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PROGRAM08.30–15.30 Member Research Consortia (MRC) and project meetings by separate invitations

15.30–16.00 Coffee

16.00–17.30 Joint session

• Industry 2030 – Megatrends that will drive changes in industry. A Swerea foresight performed together with Kairos Future, Mats Lindgren, Kairos Future.

• Industry 2030 – How does it impact Swerea KIMAB? Reflections from management.

• Four highlights from current work1. Additive manufacturing – The road from prototypes to products, Annika Strondl, Swerea KIMAB and Åsa Gustafson, Scania

2. The Sundsvall Bridge – New type of foundation, new corrosion issues, Bertil Sandberg, Swerea KIMAB and Ove Malmberg, Trafikverket

Mats Lindgren, CEO and Founder of Kai-ros Future. He has extensive experience within management, strategy, foresight and innovation. Mats has held several thousand international lectures.

GENERAL [email protected]

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Members’ day 18 November 2015 in Stockholm

3. Local measurements of hydrogen in steel and coated steel – Development of a new technique, Dominique Thierry, Institut de la Corrosion

4. In-situ study of high-temperature phase equilibria in duplex stainless steels at Lucas Heights, Sydney, Niklas Pettersson, Swerea KIMAB

17.30–18.30 Mingle and laboratory tour

19.00 Dinner

TECHNICAL DISCUSSIONFor member company representatives only participating in the joint afternoon session, there will be representatives from Swerea KIMAB management available between 13.00–15.00 for a presentation of the institute and technical discussions.

PROGRAMME AND REGISTRATION are available on www.swerea kimab.se.

Claude DuretThual, general manager of Institut de la Corrosion in St Etienne, was presented with the prestigious CEFRACOR Award at CEFRACOR’s annual general meeting.

In connection with the meeting, Claude gave a presentation of her experiences of trials in the testing laboratory. The award is in recognition of Claude’s contribution to corrosion research in general, and the development of testing methods for stainless steel and other highalloy material in [email protected]

CEFRACOR Award goes to Claude Duret-Thual

BRASS ALLOYS 2016 creating an interna-tional arena for presentations and informa-tion exchange, aiming to boost and facilitate on-going and future research work in the field of brass materials and processing.

Main Topics• Process development and optimisation• Alloy and product development• Corrosion properties and testing• Forming and machining• Recycling and refining

MORE INFO: www.swereakimab.se

Brass Alloys 2016Stockholm, Sweden

25–27 May 2016

in short


THE CORROSION RESISTANCE for high and low alloyed steels is essentially different. The best stainless steel alloys on the market today have good corrosion properties. A common way to rank the susceptibility to localized corrosion is by using chloride solutions and to evaluate how the materials interact with the solution. The Critical Pitting Temperature, CPTvalue, is commonly used to rank stainless steels in 1 M NaCl and the method is standardised according to ASTM G150 and ISO 17864.

The materials used today are getting more and more highly alloyed which implies better corrosion resistance. However, the ASTM G150 and ISO 17864 methods have temperature limitations in upper temperature and are therefore not applicable to these types

New equipment at Swerea KIMAB Electrochemical measurements of high-alloyed materials

LENA SJÖGREN, Swerea KIMAB, has been elected convenor of ISO TC35 SC12 WG2, “Prepara-tion of steel substrates before application of paints and related products”, subcommittee 2 “Surface cleanliness”.

A working group may be established by an ISO technical committee for a specific task, in this case standards covering methods to evaluate the state and cleanliness of surfaces before painting. The group consists of a number of experts from different countries. Working group convenors are ap-pointed for up to three years and are responsible for leading the work, and reporting to the technical committee.

The former convener of this working group was Carl Appelgren, Scania.

CPT-measurements (double samples) performed on a highly alloyed stainless steel in 1M NaCl, 50bar. The pitting corrosion attack after exposure is also shown.

Jesper Flyg, researcher at Swerea KIMAB, with the new equipment.

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New convenor of ISO TC35 SC12 WG2

of alloys. Swerea KIMAB has therefore developed a new electrochemical equipment that can be used to rank highalloyed stainless steels and Nibase materials.

– With this equipment we was can expose the material in an aggressive solution and perform electrochemical measurements up to approximately 200 °C, says Jesper Flyg, researcher at Swerea KIMAB

Both pitting potential, critical pitting temperature and critical crevice temperature can be carried out. Measurements have been performed on highly alloyed stainless steel and nickel based materials. Depending on the conditions, different sample designs can be used.



Swerea KIMAB has together with 4S Led-ningsnät developed an inspection course with focus on welded polyethylene (PE) pipes in the water industry. The course is mainly targeted at foremen and technical consultants as well as engineering and installation contractors and the overall ob-jective is to increase the knowledge of PE piping systems and to ensure the quality of the material and welds. The first course was held in Gothenburg in late October with approximately 20 participants from local water supply network owners.

4S Ledningsnät is an industry organiza-tion consisting of municipal water and sewerage companies in Scandinavia. The organization was started by municipalities after experiencing problems with piping materials (such as PE). Over the next 25 years, large investments are planned and

therefore it is important to ensure correct quality before start-up, as well as correct maintenance and renovation.

The aim of the course is to educate inspectors to evaluate pipes and per-form weld integrity assess-ments. Highlights from the course include; properties of polymers (with focus on PE), standards, requirements, control of delivered pipes, welding of plastics, common failures in plastic welding, working environment, non-destructive and destruc-tive testing of pipes, and drinking water hygiene. The course includes theoretical and a practical parts.


Course for inspectors of plastic water and sewage pipes

Leaking pipes can lead to enormous costs, especially when the pipes have to be dug out.

Swerea KIMAB now offers courses for plastic welders according to European Welding Federation guidelines EWF 581 and certifica-tion according to EN 13067. Depending on the experience level of the participants, the course is either a 3-day or a 5-day course. In both cases the course includes theoretical and practical parts.

There is a growing demand on quality assur-ance in many areas. For metallic materials and welding of metals stringent requirements have been in place for many decades. Quality assur-ance of plastic materials, and especially plastic welds, is a field of less experience and control compared to metals but requirements from weld-ers as well as users and owners are increas-ing. Swerea KIMAB has developed the plastic welding courses based on extensive experience of plastic materials for corrosive environments, plastics for water and sewerage, and plastic welding.

The shorter 3-day course is for experienced welders with at least 2 years of experience. The extended 5-day course is intended for beginners within plastic welding, thus offering a quicker way to certification. Both courses focus on butt welding and electrofusion welding of polyethyl-ene pipes.


Plastic welding certification courses

Next course:February 9–11, 2016

More info & registration:www.svensktvatten.se

Next course:January 27–29, 2016

More info & registration:www.swereakimab.se

new courses

Tensile testing of welds: Brittle failure mode at the top and the desired ductile failure mode at the bottom.


SURFACE TREATMENT COURSE

FROSIO CERTIFICATION

Plastic repair welding – unchartered territory…until now!There are many standards for plastic welding; however, they only cover welding in new plastic material/equipment. At Swerea KIMAB there has been a focus on welding of materials/process equipment exposed to chemicals during service for some time. In a recent collaboration project between Swerea KIMAB and Materi-als Technology Institute (MTI), a large practical study within welding of chemically exposed materials/process equipment has been performed. Through this study a lot of experience has been collected for welding of different plastic materi-als exposed to different environments. Another outcome has been a better fundamental understanding of the reason of poor weldability in used process equipment, and in some cases better techniques for repair welding have also been found.

During the project much information has been obtained regarding welding of plastic materials including PE, PP, PVC, CPVC, PFA, PVDF etc. exposed to chemicals such as HCl, H2SO4, HNO3, HF, NaClO etc. for certain times and temperatures. In the study, samples exposed both in the lab and in long term ageing in the field have been used for the welding trials. For evaluation of the welding quality visual inspection, short term weld factor from tensile testing, energy factor, peel testing and fatigue testing have been used and compared.

The report from the project contains a lot of results, conclusions, recommendations and guidelines when it comes to welding of plastics exposed to chemicals. There are also many pictures describing different types of typical defects, like bubble formations and cracks in and around the welds, and their influence on the weld performance. Furthermore, stress-strain curves with calculated weld factors are presented for a large number of combinations of plastics and types of exposures.

Order the book at: http://mtiproducts.org/

March 7–11, 14–18, 2016 Stockholm, Sweden

Teknologisk Institutt (TI) in Oslo will in March 2016 give its 2-week course for certification of inspectors for paint systems and surface treatment at Swerea KIMAB premises in Kista, Stockholm. Through placing the course in Swe-den, TI and Swerea KIMAB among others hope that more Swedish people will attend this course, whose contents and requirements for approval are regulated in the Norwegian Standard NS 476.

The goal of the course is to give the participants sufficient theoreti-cal knowledge and practical exercises in order to qualify them to perform independent inspections on items where paint systems have been used as corrosion protection. Also included in the course is an understanding of how different environments can affect objects and the measures used to protect from corrosion.

INFORMATION AND REGISTRATIONwww.swereakimab.se

Plastic Repair Welding

Daniel Ejdeholm, Marie Allvar, Karin Jacobson

Plastic Repair Welding

Marie Allvar, Daniel Ejdeholm

, Karin Jacobson

CalendarNovember 17–18, 2015 LIGHTer International Conference 2015 Location: Gothenburg Sweden

More information at www.swereakimab.se

November 18. 2015 Swerea KIMAB Member Day 2015Location: Swerea KIMAB, Stockholm, Sweden


November 19. 2015 Coatings for Corrosion Protection in Marine & InfrastructureLocation: Swerea KIMAB, Stockholm, Sweden


December 8. 2015 Korrosion i förbränningsanläggningarLocation: Swerea KIMAB, Stockholm, Sweden


February 9–10. 2016 Ytskydd 2016Location: Gothenburg, Sweden

More information at www.ytskydd.com

May 11–12. 2016 Members’ days in BrestLocation: Brest, France

More information at www.institut.corrosion.fr

May 25–27. 2016 Brass Alloys 2016Location: Stockholm, SwedenCourses


SWEDEN

Plastic welding certification courses January 27–29, 2016

Course for inspectors of plastic water and sewage pipesFebruary 8–11, 2016

Surface Treatment CourseFROSIO CertificationMarch 7–11 & 14–18, 2016

The beauty of rust - Swerea | Fem forskningsinstitut för · PDF file ·...

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