Optimizing additive Y₂O₃ concentration for improving corrosion resistance of ceramic coatings formed by plasma electrolytic oxidation on Zr-4 alloy

Abstract

The corrosion resistance of ceramic coatings developed by plasma electrolytic oxidation (PEO) can be improved by embedding particles. Optimizing the concentration of particles in the electrolyte is essential to obtain the best coating performance. This work aims to optimize the concentration of Y2O3 embeded in the PEO coatings on Zr-4 alloy to obtain the best corrosion resistance. Nanoparticles Y2O3 was suspended in the PEO electrolyte at a concentration of 2-4 g/l. PEO was conducted in a phosphate-silicate-based electrolyte at a constant DC current mode of 400 A/m2 for 10 min. The corrosion resistance was evaluated in a 4000 ppm H3BO3-2.5 ppm LiOH solution, and the high-temperature oxidation was studied in air at 600°C. The electrochemical and oxidation tests revealed a consistent result that the particle enrichment in the coatings enhanced corrosion resistance. The highest corrosion resistance was obtained for the coating formed in the 3 g/l Y2O3-containing electrolyte. The reason was related to the reduction of surface roughness and an increase in the tetragonal (t) ZrO2 phase. Moreover, the particle embedment on the coating surface ennobled the corrosion potential.