The effect of chloride ions on the corrosion and passivation behaviour of cadmium

THE CORROSION and passivation behaviours of cadmium in aqueous solutions of different pH were investigated. The effect of chloride ions and their concentration on the electrochemical behaviour of the metal was studied. The corrosion parameters, corrosion current density (i(corr)), corrosion resistance (R-corr), and corrosion potential (E-corr), were calculated. The effect of concentration of chloride ions on the values of these parameters in acidic (pH = 1), neutral (pH = 7), and basic (pH = 13) aqueous solutions was traced. Open-circuit potential measurements, polarization experiments, and electrochemical impedance spectroscopy (EIS) techniques were used. X-ray photoelectron spectroscopy (XPS) and scanning-electron microscopy (SEM) were used to investigate the metal surface before and after treatment with the chloride-containing solutions. The results of the surface analysis are consistent with the measured corrosion characteristics. The mechanism of the corrosion/passivation phenomena occurring at the electrode/electrolyte interface in the different solutions is discussed.