Characterization and corrosion behavior of plasma electrolytic oxidation coating on zirconium alloy in superheated steam condition

The plasma electrolytic oxidation (PEO) coating on Zirconium (Zr) alloy was employed and immersed under 400 degrees C/10.3 MPa steam conditions. The surface morphology, phase composition, microstructure, and element distribution of the PEO coating after corrosion were analyzed. The results indicate that the PEO coating presents lower corrosion weight gain because the compact oxide layer on the PEO coating presents few cracks and pre-vents the corrosion media from entering the substrate. The compact oxide layer is caused by the high compressive stress in PEO coating, which is helpful for the nucleation of t-ZrO2 grain and restricting the phase transformation from t-ZrO2 to m-ZrO2, thus reducing the volume expansion and defects. Based on the XRD, SEM, XPS, Raman mapping, and TEM results, the corrosion mechanism and phase transformation processes of the PEO coating under 400 degrees C/10.3 MPa conditions were summarized.