Electrochemical activation of the electroless deposition of Ni–P alloy and phase structure characterization of the deposit Part II: Single bath system

Abstract

The process of electroless Ni plating (EP) was activated by the cathodic deposition of precursors of Ni in the same bath in which EP takes place. The current density (c.d.), duration of cathodic activation, as well as the duration of subsequent EP were varied and the effect of these parameters on the phase composition of the resulting Ni–P deposits was determined by anodic linear sweep voltammetry (ALSV). It was found that electrochemical activation can be achieved with relatively low c.d. and short current pulses, to run at rates comparable to EP activated in other ways. The rate of EP alone was found to be in the range between 1 and 5 mC cm⁻² s⁻¹, regardless of the activation c.d. or the amount of electrochemically deposited Ni precursors. A synergistic effect was obtained in cases when a little low c.d. cathodic current was passed simultaneously with the EP. The alloys were found to consist of a solid solution of P in Ni, as well as of some phosphide compounds and pure Ni (at increasing activation c.d.). During EP, however, only the solid solution was deposited. The phase structure of the deposit can be varied to a certain extent by the activation c.d.