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Evaluation of the Durability of Weathering Steel – Effects of environmentals changes on corrosion behavior of low alloyed steels.
Author(s) -
Morel JeanMichel,
Creus Juan,
Gaillet Laurent,
Chatel Vincent,
Astic JeanYves
Publication year - 2021
Publication title -
ce/papers
Language(s) - English
Resource type - Journals
ISSN - 2509-7075
DOI - 10.1002/cepa.1468
Subject(s) - corrosion , durability , metallurgy , context (archaeology) , materials science , weathering , structural material , coating , composite material , geology , paleontology , geomorphology
Weathering steels are structural steels mainly used in civil engineering structures like bridges, building and in some electrical network structures. These steels that are slightly alloyed with copper and chromium have the advantage of not requiring a protective coating because of their good atmospheric corrosion resistance compared to conventional steels. This protection prevents repainting of structures which is the main maintenance operation of them with large drawbacks from a sustainable development point of view (economy, ecological, social). Besides a lack of understanding of how the distribution of chemical alloying elements act to reduce the corrosion rate, an important limit of their use remains in the ability to predict their corrosion behavior in a coupled environment/steel grade context. Furthermore, the two main atmospheric pollutants known to have a major influence on corrosion of structural steels are SO2 and chlorides. In recent decades, SO2 levels have drastically decreased in the atmosphere. During this same period the sulfur content in steels, which is the most harmful chemical element from the point of view of atmospheric corrosion, decreased sharply. The evolution of these both parameters could have an influence on the prediction models for the long‐term durability of steels. We are carrying out an experimental campaing aiming to characterize and model formation of patinas on different grades of steels exposed on several atmopsheric sites. Exposure times range from short term (a few weeks to several years on 6 different grades in 6 sites of different environments) to long term (samples taken from structures erected since few decades). These different samples were characterized according to a multi‐scale approach by metallographic techniques (macros‐copy, microscopy and fractography) and, microstructural (Raman and XRD), electrochemical and gravimetric techniques. The results after 1 year of exposure show very close corrosion rates whatever the non‐marine environments considered and there are no significant differences between the different grades of steel. From the point of view of their structures, the patinas present a double‐layer appearance, including for conventional steels.