Air Oxidation of a Ni‐P Alloy

We have studied the oxidation of an electroless‐plated, amorphous Ni‐19P alloy at temperatures from ambient to 300°C. At 200°C and below, the reaction follows logarithmic kinetics, and the oxidation product attains a limiting thickness ranging from approximately 6Å at room temperature to 15Å at 200°C. At 300°C, the reaction obeys a parabolic rate law. The oxidation product has a layered structure. At room temperature and 100°C, and also at 200°C for oxidation times less than is required to attain the limiting thickness, the product consists of an outer layer and an inner nickel phosphate layer. In the temporal region of the limiting thickness, the hydroxide gives off water slowly to form . At 300°C, , , and a nickel phosphate are present at all oxidation times with the layer growing between the hydroxide and phosphate layers.