Corrosion behavior of deep cryogenically treated AISI 420 and AISI 52100 steel

In this work, the impact of deep cryogenic and tempering treatment on the corrosion behavior of AISI 420 (UNS S42000) and AISI 52100 (UNS G52986) steel in 3.5% sodium chloride (NaCl) and sodium bicarbonate (NaHCO3) + 0.25% NaCl solution was studied using open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) measurements. The relationship of microstructure and the electrochemical response of differently treated samples was discussed. The results indicated that, compared with the conventional treatment, no significant modification of the electrochemical corrosion behavior after cryogenic treatments was observed. No passive behavior was observed for either AISI 420 or AISI 52100 in 3.5% NaCl, whereas it was observed in NaHCO3 + 0.25% NaCl solution. Different effects of tempering treatment on the corrosion behavior between AISI 420 and AISI 52100 were observed due to different modifications of the microstructure during the tempering process. The amount of retained austenite has a critical role in determining the pitting resistance. The pitting resistance increased with the amount of retained austenite.