CORROSION PERFORMANCE OF PLASMA NITRIDED AUSTENITIC STAINLESS STEEL IN PHOSPHATE SOLUTIONS AT pH=6.0

Austenitic stainless steel has good corrosion resistance, but its low hardness limits use whenever surface hardness is required. Plasma nitriding is a well established technique for steel hardening that can also be applied to this kind of steels with the aim of enhancing its hardness. Austenitic stainless steel sample was plasma nitrided at a temperature of 530 degrees C for 14 hours. Electrochemical corrosion studies were carried out with disk electrodes of nitrided austenitic stainless steel in phosphate solution at 6.0, using cyclic voltametry and electrochemical impedance spectroscopy (EIS) technique, comparing the results with those for untreated austenitic stainless steel. Very low corrosion current densities and passive current densities were obtained from the polarization curves, for untreated and nitrided austenitic stainless steel samples. The EIS technique was applied to study the nature of the passive film formed on untreated and nitrided austenitic stainless steel samples in phosphate solution, at open circuit potential. The results confirm that the corrosion resistance of the studied nitrided austenitic stainless steel in phosphate solution at pH 6.0 are better or similar to those of untreated austenitic stainless steel.