Electrochemical characterisation of the porosity and corrosion resistance of electrochemically deposited metal coatings

Electrochemical techniques for the assessment of porosity in electrodeposited metal coatings are reviewed. The determination of porosity and corrosion, resistance is illustrated by electrochemical data from three coating/substrate systems namely: electroless nickel on aluminium and steel and immersed gold coatings on an electroless copper-plated ABS polymer. Nickel coatings were up to 24 μm thick while gold deposits had thickness between 75 and 190 nm. Tafel extrapolation and linear polarisation resistance methods were used to determine the corrosion rate of the coated substrates. The aluminium samples were tested in 5% w/v (0.85 mol dm− 3) NaCl, while coated steel and ABS samples were immersed in 0.125 mol dm− 3 H2SO4 and 0.1 mol dm− 3 NaBH4, respectively, at 295 K. Current vs. time curves and anodic polarisation behaviour have also been considered.