The application of an electrochemical technique to determine the porosity of electroless nickel coatings produced in hypophosphite baths

An electrochemical polarisation technique was employed to measure the porosity of electroless nickel (EN) coating. The technique is based on the change observed in the electrochemical parameters with varying cathode and/or anode area on a bimetallic corroding surface. The nickel coating test samples were obtained from a hypophosphite plating bath in the presence of different complexing agents. This technique was used to estimate the effect of coating thickness on porosity and the influence of addition of different complexing agents to EN baths on porosity. The results suggest that, unlike other conventional methods, the electrochemical, a non-destructive method, can detect the smallest pore in an EN-coating and quantify its size in terms of pore area fraction.