Bath Optimization and Corrosion Study of Ni-P on Zincated Aluminium from Glycine Bath

Electroless deposition is a fascinating technique by which smooth, uniform and highly adherent deposits can be obtained. It is one of the best and cost effective method. In this method, nickel-phosphorus (Ni-P) coatings were formed on aluminium alloy in an electroless glycine bath with various deposition conditions. The bath constituents such as nickel sulphate, glycine, sodium hypophosphite and bath parameters such as pH, temperature, surface area/volume ratio and plating time were optimized by changing the above to get better quality of nickel deposits on aluminium. In this process, nickel sulphate was used as metal ion source, glycine as a complexing agent and sodium hypophosphite was used as a reducing agent. The thickness and rate of deposition were measured from the weight of the Ni-P deposits. The corrosion resistant properties of the coatings were studied by Tafel polarization and electrochemical impedance spectroscopy (EIS). The electrochemical analysis in 3wt. %NaCl solution provided that, the Ni-P coating exhibited better corrosion resistance than the bare aluminium alloy substrate.