The effect of substrate minor compositional differences on the corrosion performance of coated steels

Abstract Cabinet tests with wet and dry cycles were undertaken to investigate the effect of small differences in the composition of steels provided by two different manufacturers on their corrosion behaviour when coated and exposed to controlled atmospheres inside a cabinet. A clear alkyd lacquer was chosen as the coating in order to facilitate the monitoring of the corrosion features. Scribed panels were exposed to two aggressive atmospheres. The first environment simulated the effect of industrial atmospheres (Prohesion test). The second environment was made up of a solution which was 10 times more concentrated than the acidic rain of Manchester. In the Prohension test, the corrosion characteristics of the coated steels obtained from different manufacturers showed distinct differences which seemed to be related to the microstructural characteristics of the various steels, mainly their inclusion content. However, the results from the acid rain test did not distinguish the various coated specimens in terms of their corrosion behaviour. The Prohesion test was more corrosive than the acid rain test. This indicates that the degree of corrosivity of the environment influences the ranking of coated specimens in relation to their corrosion performance.