Relationship Between Microstructure and Marine Corrosion Resistance of Martensitic Stainless Steels: A Multiscale Approach

摘要

The electrochemical properties of martensitic stainless steels may depend on complex aspects of their microstructure. Three alloys were considered in this study: X30Cr13 (AISI 420), a martensitic stainless steel with a low content of alloying elements; X17CrNi16-2 (AISI 431), chosen for its strong resistance to corrosion; and X5CrNiCu15-5 (AISI 630), chosen for its good mechanical resistance. Voltammetry tests have shown the influence of carbon and chromium content on corrosion resistance. Resistance to pitting appears equivalent for the both. However, heterogeneous corrosion, in relation to delta-ferrite precipitation and chromium carbides at the lath boundaries, appears in the case of X17CrNi16-2. Conversely, non-preferential corrosion occurs in the case of the X5CrNiCu15-5, and a superior passive film stability during immersion in artificial seawater. This counterbalance negative effect of the microstructure. Thus, it achieves an equivalent macroscopically corrosion behavior between the two steels.