Waterside corrosion of M5 alloy in lithiated/borated and supercritical water: Influences of aqueous environments

The corrosion characteristics of M5 alloy in lithiated/borated water and pure supercritical water were investigated. Oxide films that formed on the alloy were primarily made up of m-ZrO2. Promoting inward diffusion of O2- into the matrix through defects, Li+ and OH- shared a synergistic effect on the occurrence and acceleration of waterside corrosion. B-(OH) and zirconium borate produced by the reaction between boric acid and OH- are conducive to alleviating LiOH ingress. In supercritical water, M5 alloy experienced weight loss. The microcrack density and porosity were significantly larger than those in the Li/B environment, and long transverse cracks parallel to the O/M (oxide/metal) interface existed. NiO, Ni2FeBO5 and NiMoO4 simultaneously deposited in lithiated/borated water, while large-sized spinel oxides were the main Ni-based deposits in supercritical water.