Effect of cathode configuration on the microstructure, corrosion resistance, and radiation tolerance of microarc oxidation coatings on zirconium alloy

Micro-arc oxidation (MAO) coatings represent an effective surface modification strategy for extending the service life of zirconium alloys in pressurized water reactors. In this study, the oxide coating was in situ fabricated on zirconium alloy surface via MAO, and the effects of the different cathode configurations on the microstructure and properties of the coating were systematically investigated. All coatings were composed of tetragonal ZrO₂ (t-ZrO₂) and monoclinic ZrO₂ (m-ZrO₂), with m-ZrO₂ being the dominant phase. Changing the cathode configuration from a plate to a ring significantly increased coating thickness, which further grew with the number of rings. The thickest coating was obtained with the 10-ring cathode configuration (MAO-4). The corrosion resistance and bonding strength of the MAO-4 coating also exhibited a similar increasing trend. The MAO-4 coating exhibited the lowest corrosion current density (3.88 × 10⁻⁷ A/cm²) and the highest corrosion potential (−0.102 V). Its bonding strength reached 13.63 N, which is 2.4 times higher than that of the coating prepared with the plate cathode. Moreover, this oxide coating exhibited outstanding radiation resistance, with damage levels reduced to 41.7 % of that of the uncoated zirconium alloy. These findings offer valuable theoretical and technical guidance for optimizing coating architectures in nuclear materials, with promising implications for improving the safety and stability of nuclear fuel cladding.