Effect of Tempering Time on Corrosion Resistance of High Co- Ni Steel

The present study attempts to improve corrosion resistant of high Co-Ni steel in ~ 1.0 wt% NaCl environment at 25 °C (room temperature) by different tempering times. Microstructures of specimens were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). The corrosion behavior was evaluated by polarization curve and electrochemical impedance spectroscopy. Firstly, the tempering time has a great influence on the morphology of martensite lath in high Co-Ni steel. Secondly, it was observed from the experimental data that a passivation/oxide layer with N-type semiconductor behavior was formed on all the samples studied in this paper. Increasing the tempering time can move the corrosion potential forward. Finally, tempering time of 16 h effectively improves the overall stability of the sample surface and reduces the corrosion tendency of the sample.