The solution annealing of cold rolled super austenitic stainless steel UN08029 alloy was carried out to investigate the role of solutionizing duration and temperature on the electrochemical corrosion and pitting resistance of the alloy. Linear polarization, cyclic potentiodynamic, and electrochemical impedance spectroscopy techniques were used to evaluate the electrochemical behavior in 3.5% NaCl solution. The microstructural analysis of the solutionized samples revealed the formation of uniform equiaxed grains from elongated columnar grains, which size increases with duration and temperature. The charge transfer resistance shows an increasing corrosion protectiveness of 46 to 60% with increasing solutionizing duration from 30 to 120 min. Similarly, a 45, 52, 60, and 26% improvement in the corrosion performance was obtained for sample solutionized at 1000, 1100, 1200, and 1300 °C, respectively. In general, the solutionized samples demonstrated improved resistance over the as-received alloy, and this behavior increases with solutionizing duration and temperature. Though the pitting potential drops below that of the as-received alloy, the hysteresis loop revealed that the solutionized samples are less prone to pitting damage, and the sample solutionized at 1200 °C for 120 min exhibited optimum pitting corrosion resistance. The microstructural influence on corrosion was also discussed.
Keywords: annealing; corrosion; electrochemical impedance spectroscopy (EIS); heat treatment; pitting; stainless steel; supersaturated austenite.