Preparation and characterization of electroless Cu–P deposition protection for mild steel corrosion in molar hydrochloric solution

Abstract

A new basic formulation of electroless Cu–P plating using sodium hypophosphite as reducing agent was developed at different concentration of NiSO₄. 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 NiSO₄ concentration and reaches 92% at 2 g L⁻¹.