Influence of Chemical and Phase Composition of Ni–P-Based Alloy Powders on the Corrosion Behavior in Various Environments

The as-prepared and thermally treated Ni–P and Ni–Fe–P alloy powders obtained by chemical reduction were studied regarding the microstructure, as an important factor affecting the functional properties of the materials. Also, the influence of the microstructure and thermally induced transformations of the studied materials on the corrosion behavior in neutral, alkaline, and acidic media is presented. For a detailed study of the mentioned phenomena, different structural and electrochemical techniques were used, including XRD, TEM, DTA, potentiodynamic, and EIS measurements. The composition and microstructure of the studied alloy powders were shown to be dependent on the reactant ratio and thermal history of the material. Small amounts of crystalline phases present in the as-prepared powders, as well as crystalline phases formed during crystallization, included some or all of the following phases: Ni, Ni₃P, and Ni₁₂P₅. It was shown that the addition of small amount of Fe into the Ni–P powder alloy considerably affects the microstructure and thermal stability of the material, having beneficial effect on the formation of protective oxide layers and thus on the corrosion resistance in chloride environments.