H<SUB>2</SUB>SO<SUB>4</SUB>-NaCl水溶液中におけるSUS304ステンレス鋼の孔食現象に及ぼす加工誘起マルテンサイトの影響

Abstract

The effect of the deformation-induced martensite (α′) on the pitting corrosion of Type 304 austenitic stainless steel in H2SO4-NaCl solution was investigated by means of electrochemical measurements and optical microscopic observation.The main results obtained are summarized as follows:(1) The pitting corrosion resistance of SUS304 steel decreases with an increase in the volume fraction of martensite. The pitting corrosion resistance also decreases with increasing solution temperature and NaCl concentration.(2) The effect of martensite on the number of pits of SUS304 steel depends upon the NaCl concentration, temperature and potential. In the case of high NaCl concentration, the amounts of pits increase lineally with increasing volume fraction of martensite in SUS304 steel. Under high temperature and high anodic potential conditions, the amounts of pits are almost constant in the range of the volume fractions of more than 50%.(3) The pitting corrosion rates increase as the concentration of NaCl, the anodic potentials and the temperature of the solution are increased. The concentration of NaCl and the anodic potentials affect the amounts and growth of pits, while the temperature affects only the amounts of pits.