Electrochemical corrosion behaviour of a novel submicron-grained austenitic stainless steel in an acidic NaCl solution

Novel microstructures consisting of various fractions of tempered martensite, retained austenite and submicron-grained austenite were processed in an AISI 301LN type austenitic stainless steel by reversion annealing of severely cold-rolled strips. Corrosion resistance of the special microstructures was investigated and compared with that of the conventional cold-rolled or annealed grades. Potentiodynamic anodic polarization study showed that the corrosion resistance in an acidic chloride solution (1 M NaCl + 0.1 M HCl, pH 1) is impaired by heavy cold working, but upon annealing it gets improved, faster in the 75% than in the 45% cold-rolled steel. The presence of martensite seems to be the factor reducing the general corrosion resistance. However, the submicron-grained structure exhibits better pitting corrosion resistance than the coarse-grained one in the acidic chloride solution and also in immersion in the ferric chloride solution, where pit initiation takes place preferably at grain boundaries. (c) 2006 Elsevier B.V. All rights reserved.