Revealing the enhanced corrosion resistance of Cr/FeCrAl-coated Zr alloy in simulated PWR water

The long-term corrosion behavior and oxide evolution of Cr/FeCrAl-coated Zr-4 alloy in simulated PWR primary water (360 °C and 18.6 MPa) were systematically investigated. Results showed that a continuous triplex oxide film, featuring FeCr 2 O 4 spinel, Fe 3 O 4 spinel and (Cr,Al) 2 O 3 , was developed on the coating, effectively protecting Zr substrate from corrosion. In the early stage, sustained outward Fe/Cr diffusion precipitated on the surface to form the outer spinel layer, while the internal (Cr,Al) 2 O 3 layer grew inwards through oxidant transport. Over time, the diffusion barrier effect of dense (Cr,Al) 2 O 3 layer shifted spinel growth mechanism to dissolution-reprecipitation, accompanied by a decelerated oxide growth. The superior corrosion resistance was dominated by the (Cr,Al) 2 O 3 layer. During exposure, the FeCrAl-Cr interface and the developed near-equiaxed Cr nanograins arrested the vertical cracks along GBs and promoted blunting/deflection, mitigating coating spallation and preserving structural integrity.