Electrochemical and weight change methods were used to study the synergistic inhibition offered by Zn2+ ions and 2 carboxyethyl phosphonic acid (2CEPA) to the corrosion of mild steel in 60 ppm chloride solutions. The surface film was found to contain Zn(OH)(2) along with iron phosphonate complex. The diffusion of iron, phosphonate complex and H+ ions through this film determines the dissolution rate of iron.