Electrochemical parameters of austenitic stainless steel after different sensitization heat treatment times

Abstract This study deals with the corrosion behavior of AISI 304 stainless steel after 10, 6, 2, 1-hour sensitization heat treatment time at the temperature of 650 °C. Sensitization of the specimens is verified by ASTM A262 practice A test. Corrosion resistance is evaluated by electrochemical parameters of the potentiodynamic polarization performed in 1M NaCl solution at the temperature 20 ± 3 °C on the specimens with high-temperature surface oxides and after their removal by pickling. The electrochemical etching test in oxalic acid confirmed the ditch microstructure and the complete sensitization after 10 and 6-hours sensitization time. After 1 hour, the material showed only slight local signs of sensitization. The electrochemical parameters of the potentiodynamic polarization were significantly affected by the state of the surface of the sensitization heat treated specimens. Regardless of the sensitization time, the specimens with high-temperature surface oxides behaved like an actively corroding metal. After pickling, they retained the passivity region, but with a higher passive current density and slightly lower pitting potential than the as received material.