Cross-effect of surface finishing and deep cryogenic treatment on corrosion resistance of AISI M35 steel

Abstract

The improvement of corrosion lifetime of commonly used steels is an important characteristic that is required for development of steel products for usage in non-traditional corrosion environments and specialized applications such as oil and gas industry. In order to achieve the required enhancements in a versatile manner, a combination of material and surface processing schemes can be used. In this research, the effect of surface finishing (original, polished, etched and immersed in LN2) on corrosion behavior of steel AISI M35 is investigated. Furthermore, the change of corrosion properties with the application of deep cryogenic treatment (DCT) is researched and compared with the effect of conventional heat treatment (CHT). The various surface finishing induce modified corrosion product development and degradation of material. The surface finishing with contributing nitrogen presence (etching and immersion in LN2) display significant suppression in development of corrosion products related to the formation of green rust. On the other hand, DCT induces microstructural and mechanical changes, which also influence the corrosion dynamics. DCT is confirmed to reduce exfoliation of the corrosion product layer due to reduced surface cracking induced by residual stress-of the microstructure. Additionally, DCT reduces pitting formation and growth, resulting from the changed alloying element concentration and microstructure. The cross-effect of both nitrogen-introducing surface finishing and DCT have the most positive influence on corrosion properties of steel AISI M35. The modifications lead to improved self-corrosion protection and stability of the surface resulting in increased durability of AISI M35 in saline corrosive media.