A new bath formulation was developed, which allowed deposition of copper-rich Cu-Ni-P alloys in electroless acidic solutions in the absence of formaldehyde. The reducing agent was sodium hypophosphite. Though cupric ions do not catalyse the oxidation of hypophosphite, we show that, in the presence of a low concentration of Ni(II) species, it is possible, even at low pHs, to induce the reduction of the cupric species. A very strong preferential deposition of copper was observed, which gives Cu-Ni-P layers with copper content up to 97 wt%. The phosphorus content decreased from 13% to 1% with increasing copper content. The plating rate decreased when the copper sulfate concentration in the solution increased. It increased with increasing pH or temperature, but the influence was less pronounced than in alkaline solutions. Compact layers were obtained with a nodular morphology which did not markedly changed with composition.

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A new basic formulation of electroless Cu-P plating using sodium hypophosphite as reducing agent was developed at different concentration of NiSO 4 . So, the effect of temperature solution, pH and immersion time on deposition rate was also investigated. It is found that the deposition rate increases with nickel sulphate concentration and temperature and decreases with immersion time. The cyclic voltammetry study showed that the electroless deposition was controlled by the anodic processes. In addition, the scanning electron microscopy (SEM) observations and energy dispersive X-ray (EDX) analysis were used to characterize Cu-P deposit. Thus, the micrograph showed that coating presents a nodular aspect and is relatively homogeneous. Finally, the corrosion protection of mild steel by this coating in 1.0 M HCl was studied using electrochemical measurements. It is found that the protection increases with NiSO 4 concentration and reaches 92% at 2 g L À1 .