Crevice and pitting corrosion of low temperature plasma nitrided UNS S32750 super duplex stainless steel

The UNS 532750 super duplex stainless steel (SDSS) was low temperature plasma nitrided at 350 degrees C and 400 degrees C for 4 h. Pitting and crevice corrosion resistance was evaluated using electrochemical techniques in a NaCl neutral solution. Nitriding treatments resulted in increased in hardness, general corrosion resistance and in the passive layer breakdown potential. Regarding crevice corrosion tests, the nitrided surfaces showed lower current densities during the potentiostatic polarization and lower corrosion depths when compared to the untreated surface. The nitrogen played a fundamental role in the passivation behavior and in the susceptibility to repassivation of localized corrosion.