Dorina Kovács

The behaviour of stainless steel bridge against corrosion 

 

 

About 40% of bridges in the United States were built from steel, in Japan alone there are more than 50,000 steel railway bridges. Corrosion can lead to the progressive weakening of steel bridges’ structures, the reduction of their static capacity and increase of the dynamic vulnerability of the bridges [1]. Different types of steel are used for bridge construction, such as carbon steels, high strength steels and from the 1960s also weathering steels.  The main damage is the appearance of rust, which can be eliminated not only by rust removal, but prevented altogether by building bridges  from stainless steel. 

 

Duplex stainless steels are increasingly used for bridges due to their good corrosion resistance and easy maintenance. Mameng at al [2] checked several bridges in their research to investigate their condition in the installation environment. 

 

Two bridges over rivers and one footbridge near the seaside was examined. In one case corrosion patches (rust) appeared on the bottom of the bridges, but it was suspected that the beam had been rested on steel trestles at some point during their production, transportation or installation. In another case, pitting was observed also on the bottom of the bridge. This bridge spans a river near the sea. The pitting was caused by evaporation of salt water, where this  steel surface was not exposed to washing by the rain. In both cases it was found that these surface defects do not affect the life of the bridge.

 

  In the footbridge, discolouration was found along the welds, but these were not corrosion patches. 

 

Figure 1. Footbridge of Sölvesborg (Sweden) [3]

Figure 2. Galvanic corrosion on the footbridge [3]

 

Galvanic corrosion can be found on cable fittings of the footbridge which was caused by the potential difference between the ‘love locks’ and the base material, but it did not affect the lifetime of the bridge. No special corrosion protection was applied to these bridges, this was left to  the innate corrosion resistance of the steel. However, there are cases when the aim is to improve the protection of the material against corrosion; weather is by far not the only corrosive medium, for example acids, alkalis and drug substances used in the chemical, pharmaceutical or food industries can also be highly corrosive. 

 

Many types of research investigate the corrosion resistance of nitrided steel to improve the protection of the surface which will be presented in Chapter 3. 

 

 

References:

[1] Shuaicheng Guo, Ruizhe Si, Qingli Dai*, Zhanping You, Yunxiang Ma, Jiaqing Wang: A critical review of corrosion development and rust removal techniques on the structural/environmental performance of corroded steel bridges. Journal of Cleaner Production (2019) 233. 126-146

[2] S. H. Mameng, A. Backhouse, J. McCray, G. Gedge: Experience of duplex stainless steels as structural materials for bridges. IOP Conf. Series: Materials Science and Engineering 419 (2018) 012018.

[3] S. H. Mameng, A. Backhouse, G. Gedge: Experience of duplex stainless steels as structural materials for bridges: Results of seven inspections in European environment. EUROCORR 2019. Sevilla. 9-13. Sept. 2019.

 

Corrosion in Europe

 

EUROCORR [1] is the most important corrosion conference in Europe, which was organized for the first time in France. It has become an annual event, which rotated between different countries from Italy, Sweden, Austria, France, Czech Republic, Serbia and finally to Spain. EUROCORR 2020 will be held in Belgium, while Hungary won the right to organize the congress in 2021. Every edition of the congress has a key theme, sometimes clearly professional, other times more intended as thought starters. Two of these deserve to be highlighted:

 

– ’Advances in linking science to engineering’ – it is an excellent reflection of today’s problems, particularly the relationship between industry and science, because not all scientific assumptions and experiments are suitable for use in industrial environments. Corrosion is a phenomenon, in which the two participants cannot live without each other: problems are born in the industries and solved by science; for example with a new coating or material for corrosion protection or a new installation design. 

 

– ‘Corrosion control for a Blue Sky’ was the conference’s mysterious slogan in 2013. Based on research, there is no evidence to support that corrosion control would protect the blue sky. Nowadays, the most current topic is global warming, to which emissions from ocean liners contribute significantly. These emissions cannot be prevented by corrosion resistance, this method only protects the ship. 

The conference discusses the results of scientists researching corrosion and corrosion control  topics like metal coatings, oil industry applications or  the modelling of corrosion mechanisms. By the way, what is corrosion? 

 

The definition of corrosion according to the ISO 8044:2020 standard is: it is a physicochemical interaction between a metallic material and its environment that results in changes in the properties of the metal, and that may lead to significant impairment of the function of the metal, the environment or the technical system, of which these form a part.

 

Steel can exhibit different types of corrosion such as [2, 3]:

– uniform and general corrosion: electrochemical corrosion on the entire surface

– localized corrosion: localized electrochemical corrosion

– pitting: localized electrochemical corrosion, which causes a surface flaw

– galvanic corrosion: due to the action of a corrosion cell

– stress corrosion: due to applied or residual stress

– intergranular corrosion: corrosion in or adjacent to the grain boundaries of a metal

– erosion corrosion: caused by high-speed flow

– fretting corrosion: oscillatory slip between two vibrating surfaces in contact

 

Stainless steels are widely used in the industry where avoiding corrosion is important. Pitting is the typical corrosion type of this steel. Appearance, effect and prevention of pitting is a popular topic among researchers, which can be read in the next chapter. 

 

References: 

[1] www.eurocorr.org
[2] ISO 8044:2020 standard: Corrosion of metals and alloys — Vocabulary
[3] R.F. Stratfull, K.C. Clear, C.F. Crumpton, J.E. Bukovatz, R.M. Weed, R.G. Pike, R.E. Hay, J.R. Clifton, H.F. Beeghly, R.G. Mathey, P.L. Todd, Corrosion and Corrosion Protection., Transp. Res. Rec. (1974).