Corrosion behavior of ca6nm in simulated geothermal brine highlighted by electrochemical impedance spectroscopy (Eis)

Martensitic stainless steel CA6NM has the potential to be utilized as a turbine blade material for geothermal power plants because of its superior mechanical properties. However, the turbine blade material for geothermal power plants must have not only superior mechanical properties but also excellent corrosion resistance. Therefore, in this study, CA6NM was modified by varying its molybdenum (Mo) and nitrogen (N) contents to improve its corrosion resistance in the geothermal environment. The Mo and N contents of CA6NM were modified as follows: CA6NM1 with 1% Mo, CA6NM2 with 2% Mo, and CA6NM3 with 2% Mo and 0.1% N. Two temperature parameters, i.e., room temperature and 60°C, and two CO2 gas parameters, i.e., presence and absence of CO2 gas, were utilized in this study. To understand the corrosion behavior of modified CA6NM in geothermal brine, the electrochemical impedance spectroscopy (EIS) test was performed in simulated geothermal brine. The results of the EIS test showed that both Mo and N can increase the corrosion resistance of CA6NM in simulated geothermal brine at 60°C.