Electrochemical activation of the electroless deposition of Ni–P alloy and phase structure characterization of the deposit. Part I: Dual bath system

Abstract

A typical low temperature alkaline bath was chosen for the investigation of the effect of electrochemical activation on the efficiency of the electroless deposition of Ni and on the phase structure of the Ni–P alloys obtained. Electrochemical deposition was separated from chemical deposition by employing a two bath sequence, the first (i.e., the bath for electrochemical activation) being free of reducing agent. It was found that an activation current density, as well as an amount of precursors at the surface larger than a critical value (0.5mA cm−2 and 8 mC cm−2, respectively) are required for the electroless process to take place. The phenomenon was explained in terms of nucleation theory. Anodic linear sweep voltammetry (ALSV) of the Ni–P alloys obtained after electrochemical activation, as well as of those obtained after chemical (Sn–Pd) activation, indicated the presence of two dominant phases, that is, a solid solution of P in Ni, and a nickel phosphide compound, most probably Ni2P. It was also shown that changes in the phase structure of the electroless Ni–P deposit upon thermal treatment may be followed by employing (ALSV).