A Review of Microstructural Effects on Pitting Corrosion in Stainless Steels

A vast literature can be found on pitting corrosion addressing the initiation and propagation of pits due to localized corrosion. However, most of is the work to date is devoted to the electrochemical and metallurgical aspects of the phenomenon. In this paper, we provide a brief review of the recent progress in characterizing and analyzing the effects of various microstructural features on pitting corrosion. The scope of the paper is limited to stainless steels in chloride-containing solutions. The review shows that initiation of pitting corrosion in stainless steels is affected by such microstructural features on the exposed surface as the crystallographic orientation, phase and grain boundaries, beside the well-known and much characterized sulphide inclusions. Similarly, pit growth kinetics and evolution has been shown to depend upon the presence of precipitates and secondary phase particles, grain boundaries, and other material interfaces. One outcome of the review is the identification of the need to complement the recent computational studies incorporating fully-coupled electrochemical, mass transfer and momentum field equations at the macroscale with similar modeling and analysis at microscale to fully understand the effects of microstructural features on stable pit growth.