Effects of microstructural evolution on the corrosion properties of AISI 420 martensitic stainless steel during cold rolling process

In this study, the impacts of plastic deformation induced by compressive stresses on the evolution of the microstructure and the resultant corrosion properties of AISI 420 martensitic stainless steel (MSS) are investigated. With multiple applications in downhole environments, AISI 420 martensitic stainless steel was chosen and cold rolling was implemented to develop preferentially textured samples of this alloy. The non-deformed samples of the base metal were cold-rolled to the deformation levels of 25% and 50%. The performed corrosion analysis herein confirmed a more stable passive layer and a higher corrosion resistance for the base metal, while the 25% and 50% rolled samples exhibited higher susceptibility to localized pitting corrosion. A detailed study of the corrosion morphology of all samples revealed the preferential pitting at the regions with a high fraction of fragmented carbides. As the deformation level increases, a higher fraction of fragmented precipitates forms in the microstructure, provoking the micro-galvanic coupling and deteriorating the corrosion resistance.