The oxidation-dissolution behavior of Cr-coated Zr alloy in high temperature water

The corrosion and dissolution behavior of Cr-coated Zr alloy were investigated in high temperature water under varying dissolved oxygen (DO) and temperatures. Results demonstrate that the oxidation and dissolution rates of Cr coatings increase significantly with higher DO levels and temperature, while the Zr substrate remains unaffected by DO concentration. At DO levels below 10 ppb, Cr coatings exhibit high stability, but at 300 ppb DO, rapid corrosion/dissolution and spallation occur. The electrochemical potential (ECP) shifts in response to temperature and DO, driving the dissolution mechanism through three distinct region: steady-state, field-assisted dissolution (FAD), and complete dissolution. During the FAD period, a porous nanocrystalline Cr₂O₃ layer with residual Cr forms, characterized by non-uniform dissolution due to preferential oxidation at grain boundaries and microstructural defects. The soluble ${\text{HCrO}}_4^{-}$ ions form at the base of the porous layer, followed by partial recrystallization at the surface, leading to the development of a thin Cr₂O₃ crystalline layer.