Study of repassivation behavior of Ni-P amorphous alloy in 3.5% NaCl solution

A new set of scratching electrode apparatus has been designed to investigate the repassivation behavior of electroless amorphous Ni-P alloy in 3.5% NaCl solution at room temperature. Results obtained show that the repassivation kinetics obeys the equation: i(t) = a1exp(-c1t) + a2exp(-c2t). For the low potential values, the oxidation of Ni occurs quickly and a stable NiOOH oxide forms on the surface. The oxide film growth follows the ionic conduct mechanism of high electric field. At higher potential, the adsorption process is rapid, and the adsorbed monolayer on the interface makes the bare surface current decrease quickly. The adsorbed anion H2PO2-effectively inhibits the dissolution of Ni site