Abstract: Zirconium alloys used in nuclear reactors undergo severe zirconium-water reaction during loss-of-coolant accidents. Conventional micro-arc oxidation (MAO) coatings, limited by their high porosity, offer insufficient protection. In this study, nitrogen was innovatively introduced into the MAO process to suppress arc concentration, thereby achieving simultaneous structural optimization and nitrogen doping of the coating. Experimental results demonstratethe successful fabricationof a dense zirconium oxide coating through this approach. The porosity is significantly reduced to 4.96% (representing a 62% reduction), surface roughness is decreased, and a tight, crack-free bond with the substrate is achieved. Simultaneously, nitrogen is incorporated into the crystal lattice, forming a characteristic Zr-O-N bonding structure. Benefiting from this synergistic optimization of the microstructure and chemical composition, the dense coating exhibits a corrosion current density as low as 1.61 × 10^-8 A·cm^-2 in a 0.1 mol/L LiOH solution, which is one order of magnitude lower than that of a conventional MAO coating. This work confirms that a nitrogen atmosphere can simultaneously facilitate structural regulation and chemical modification, providing a new pathway for developing high-performance accident-tolerant zirconium alloy cladding coatings.

Key words: zirconium alloy, micro-arc oxidation, nitrogen doping, corrosion resistance