Porosity and Corrosion Rate Measurements for Electroless Nickel Deposits on Steel Using Electrochemical Techniques

Abstract

SummaryElectrochemical techniques are described for the assessment of porosity in electroless nickel deposits on steel substrates from hypophosphite baths. Methods evaluated include the monitoring of the corrosion potential, determination of corrosion rate of coated samples (by a linear polarisation resistance technique, by Tafel extrapolation of polarisation plots and by the use of anodic polarisation curves) in 0.125M H2SO4 at 22°C. The shapes of the porosity vs. coating thickness curves were similar for all the methods investigated and the porosity increased markedly in the case of thinner deposits.