Corrosion of copper in 3% NaCl solution polluted by sulphide ions

The effect of sulphide addition on the corrosion of copper in 3% NaCl was studied. The concentration of sulphide was kept rather low, up to 10 ppm. The effect of sulphide on the copper corrosion is controversial in the literature, and worth to verify by means of various experimental techniques. The polarisation curves, plotted from a potential close to the open circuit one to negative or to positive direction indicated a decrease of corrosion current density, whereas a quartz crystal microbalance indicated an acceleration of corrosion rate with increasing sulphide ion concentration. The reduction of corrosion product in boric-borate buffer solution allowed establishing that the thickness of corrosion product increased slightly when the sulphide concentration is higher. The EIS measurements showed a slight increase of corrosion rate by addition of sulphide ions, in agreement with EQCM experiments.