Dissolution of Glassy Ni‐P Alloys in H 2 SO 4 and HCl Electrolytes

Abstract

The effect of alloyed P on the dissolution of Ni was investigated with glassy Ni‐P alloys. The anodic behavior of Ni‐P in and differed substantially from that of Ni. In , glassy Ni‐P passivated at potentials up to several hundred mV anodic to , whereas Ni dissolved in the active state at comparable anodic overpotentials. At higher overpotentials, Ni‐P underwent transpassive dissolution, but Ni passivated. The behavior of Ni‐P in was virtually identical to that in , but Ni pitted severely in at small anodic overpotentials. The kinetics of passivation of Ni‐P did not vary over a range of chloride concentration from 0.2 to 3.0N, and the alloy completely resisted chloride‐induced pitting at potentials below about 800 mV(SCE). Coulometric and gravimetric measurements indicated that, during dissolution of Ni‐P at passive potentials, the P was not oxidized as completely as it was during polarization at transpassive potentials.