Study on Electrochemical Corrosion Behavior of Co Base Super-alloys in Chloride Solution

The Co base super-alloys after heat treatment were studied, and its corrosion resistance in chlorine solution was evaluated by electrochemical methods. The surface morphology of Co base super-alloys was observed by Scanning Electron Microscope (SEM) before and after corrosion property tests. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to study electrochemical corrosion behavior of Co base super-alloys in chlorine solution. The results show that the typical 11 phase is found after the heat treatment of the Co base super-alloys, and the 11 phase appears as a light gray blocky morphology. The results of potentiodynamic polarization and EIS experiments show that the Co base super-alloys have the characteristics of a typical passivation metal. The potentiodynamic polarization experiment results show that the passivation range is -0.3V to 0.4V. The observation of the surface morphology shows that the 11 phase of the Co base super-alloys has severe pitting corrosion. The corrosion not only expands along the substrate around the 11 phase to form a groove, but also the corrosion holes continue to penetrate into the substrate and present a spiral shape.