Electrochemical, surface analytical, and spectroscopic study of passive film and pits formation on food grade ferritic stainless steel AISI-430 in aqueous acetic acid containing chloride ions

Abstract

Pitting corrosion of food grade ferritic stainless steel AISI-430 was studied in 20% aqueous acetic acid solution containing 0.5 M NaCl. Potentiodynamic polarization measurements at a slow scan rate reveal formation of metastable pits and repassivation. Surface analysis reveals remnants of the passive oxide layer adhered along the circumference of the pits, evidences of loss of microcrystallites, no significant loss in crystallinity during corrosion process and formation of mixed oxides of iron and chromium. The pitting of ferritic steel is an autocatalytic process, and the proposed mechanism suggests that both chloride and acetate ions play important role. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim