Unveiling the Corrosion Mechanism of the Ni_<i>x</i>Se_<i>y</i> Intermetallic Compound in Water-Based Solution

In this study, Ni-Se intermetallic compound coatings were fabricated using electrodeposition at various process temperatures (40-70 °C). The results show that increasing the process temperature promotes the deposition of Se, which leads to a transition in the crystal phase of the samples from the Ni_0.85Se phase, prepared under low-temperature conditions, to a NiSe₂ phase. The dissolution rate of Se in pure water from Ni-Se coatings is inversely related to the incorporated Se content, which indicates that the Ni_0.85Se phase has a higher natural corrosion rate compared to the NiSe₂ phase. Under the influence of an electric field, the corrosion behavior of Ni-Se coatings is dominated by a two-stage reaction involving Se transformation and dissolution. Coatings with a predominant Ni_0.85Se phase exhibit more severe corrosion behavior compared to those with a predominant NiSe₂ phase, which suggests that the corrosion reaction is enhanced by the electric field. However, because coatings with a predominant NiSe₂ phase contain a higher proportion of Se₂^2- ions, the dissolution reaction of SeO_<i>x</i>, generated during the electrochemical reaction, is retarded, thereby inhibiting the progression of the corrosion reaction. Consequently, coatings with a predominant NiSe₂ phase exhibit relatively better corrosion resistance in a water-based electrolyte.