Synergistic effect of ethyl phosphonate and Zn2+ in low chloride media

Abstract

The synergistic effect of sodium salt of ethyl phosphonic acid (EPA) and Zn2+ on the inhibition of corrosion of mild steel in neutral aqueous environment containing 60 ppm Cl– has been evaluated by the weight-loss method. The formulation consisting of 300 ppm EPA and 300 ppm Zn2+ has 88 per cent inhibition efficiency. The nature of the protective film formed on the metal surface has been analysed by x-ray diffraction, FTIR, uv-visible and luminescence spectra. The protective film is found to be luminescent and to consist of Fe2+–EPA complex, Zn (OH)2 and a very thin film of oxides of iron.