Synergistic and antagonistic effects existing among polyacrylamide, phenyl phosphonate and Zn2+ on the inhibition of corrosion of mild steel in a neutral aqueous environment

The corrosion rates of mild steel in neutral aqueous environment containing 60 ppm chloride in the absence and presence of polyacrylanide (PAA), phenyl phosphonate (PPA) and zn2+ have been evaluated by the weight-loss method. The formulation consisting of 50 ppm PAA and 50 ppm Zn2+ and also the 50 ppm Zn2+ -300 ppm PPA system show synergistic effects (the inhibition efficiency of the latter is not decreased by addition of 50 ppm PAA) while the formulation consisting of 50 ppm PAA and 300 ppm PPA shows an antagonistic effect. The protective film has been analysed using X-ray diffraction measurements, FTIR and luminescence spectra