Influence of Cryogenic Treatment on the Corrosion Properties of 42CrMo Low Alloy Steel

In this paper, the effect of deep cryogenic treatment on the corrosion resistance of 42CrMo low alloy steel is investigated and compared with conventional heat-treated counterparts. The low-temperature treatments of the cryogenic process are −120 °C, −160 °C, and −190 °C, respectively. Electrochemical corrosion tests show that the self-corrosion current density of −120 °C, −160 °C and −190 deep-cooled specimens is reduced by 38%, 20% and 30% respectively compared to the usual heat-treated specimens. Scanning electron microscope analysis shows that the precipitation of fine carbides on the surface of the samples treated at −120 °C has improved their corrosion resistance. Electrochemical impedance spectroscopy also shows that the samples treated with −120 °C cryogenic treatment have the smallest corrosion tendency. At a −160 °C deep-cooling process, the precipitated carbide aggregation limits the corrosion resistance of the material. The corrosion resistance of the samples in the −190 °C process group is between the two. The simulation results also express a similar trend to the electrochemical corrosion results.