Zinc corrosion protection with 1,5-diphosphono-pentane

A set of identical measurement was performed to characterize the corrosion behaviour in Na2SO4 solution and surface structure of layers formed in aqueous and ethanol solutions of 1,5-diphosphonic acid on mechanically polished zinc substrates in order to understand the inhibition mechanism. Although, the protective layers formed in ethanol and in aqueous solution show substantial differences, their protection efficiency tends to the same value after about 4 h in corrosion tests. Based on EIS, XPS and GD-OES data, a simple oxide–hydroxide/diphosphonate model of the interface is proposed.