Electrochemical Properties of 316L Stainless Steel and 690 Alloy in NaOH Solution

The electrochemical behaviors of passive film formed on 316L stainless steel and 690 alloy in NaOH solution were studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements. The results showed that there were significant differences between polarization curves of the two materials in NaOH solution. 316L stainless steel had a wide passive anodic region from 100 mV to 900 mV in NaOH solution. The impedance value of the passive film on 316L stainless steel in NaOH solution was similar to that of 690 alloy. Potentiodynamic electrochemical impedance spectroscopy (DEIS) results demonstrated that with the increase of potential the variation trend of passive film was different. The results of the DEIS were in accordance with the potentiodynamic polarization curves. Mott-Schottky analysis showed that EFB of the passive film on 316L stainless steel in NaOH solution was 0 V, however EFB of the passive film on 690 alloy in NaOH solution was -0.3 V. The properties of the film formed on 690 alloy in NaOH solution were different from those on of 316L stainless steel.