The effect of sulphide ions on the corrosion inhibition of copper in acidic chloride solutions

The corrosion behaviour of copper in dilute HCl solution of pH 1.8‐2, in the absence and presence of different additives of Na₂S, was studied by open circuit potential measurement, scanning electron microscopy and polarisation techniques. A complete covering of the surface with the strongly chemisorbed HS⁻ is achieved at ≥10 ppm Na₂S concentration. The addition of different concentrations of ethylene diamine (EDA) to HCl of pH 1.8‐2 promoted the dissolution rate, due to an increase in autocatalytic dissolution at the Cu metal surface. However, the synergistic inhibition effect between EDA and Na₂S, resulting from the adsorption of HS⁻ on the Cu metal, facilitated the adsorption of EDA.