In-Situ Electrochemical Corrosion Behavior of Nickel-Base 718 Alloy Under Various CO2 Partial Pressures at 150 and 205 °C in NaCl Solution

Abstract

The electrochemical corrosion behavior of nickel-base alloy 718 was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization techniques at various partial pressures of CO2 ( $$P_{{{\text{CO}}_{2} }}$$ s) in a 25 wt% NaCl solution at 150 and 205 °C. The passive films composed of FeCO3 exhibit good corrosion resistance with a feature of Warburg impedance, Tafel plots show a complete passivation and the anodic reactions was dominated by a diffusion process at low $$P_{{{\text{CO}}_{2} }}$$ s (1.8–9.8 MPa) at 150 °C. While numerous dented corrosion areas appeared on the sample surface for the $$P_{{{\text{CO}}_{2} }}$$ of 11.6 MPa at 205 °C, the Tafel plot with three anodic peaks and the Nyquist diagram with an atrophied impedance arc were present. This dented corrosion attribute to the synergistic effects of stress, temperature, $$P_{{{\text{CO}}_{2} }}$$ and Cl−, the temperature and stress could play crucial roles on the corrosion of the alloy 718.