Preferred corrosion and its effect on delamination of steel

This paper presents the discovery of the most severe form of corrosion induced degradation of steel - delamination. The causes and effects of preferred corrosion of steel are quantitatively determined through a comprehensive experimental program and detailed analysis of steel microstructure. A large number of simulated corrosion tests are conducted by immersing steel in acidic solutions to acquire new understanding of the corrosion process of continuously cast steel. Three microstructural characteristics that affect the corrosion resistance of steel are quantified: grain size, phase composition and distribution of impurities. The results and their analyses presented in the paper indicate that preferred corrosion occurs at locations of steel where the grain size is larger; there is less cementite and more impurities. The analysis of causes and effects of the preferred corrosion provides insight into the prevention of preferred corrosion from the steel making process through to the delamination of steel in structures. This information could be used to predict, mitigate or avoid catastrophic failures of structures made of steel, potentially saving lives and resources, whilst advancing the knowledge in corrosion science of steel and improving the manufacturing process of steel.