A study on the localized corrosion of cobalt in bicarbonate solutions containing halide ions

The localized attack of cobalt in bicarbonate aqueous solutions containing halide ions was investigated using electrochemical techniques, scanning electron microscopy, UV-visible and Raman spectroscopies. Rotating disc and rotating ring-disc electrodes were used to determine the effect of bicarbonate concentration, solution pH, nature and concentration of the halide ions, convection and potential sweep rate on the corrosion processes. These parameters were found to play a key role on the localized attack induced by halide ions by influencing the production of a Co(HCO3)2 precipitate on the pit surface. Potentiostatically generated cobalt oxide films (CoO and Co3O4) were found to be efficient to reduce pitting corrosion of cobalt.