Mechanism of corrosion inhibition by the 2‐chloroethyl phosphonic acid – Zn²⁺ system

The synergistic effect of sodium salt of 2‐chloroethyl phosphonic acid (2‐Cl EPA) and Zn²⁺, in controlling corrosion of carbon steel in a neutral aqueous environment containing 60ppm Cl^–, was evaluated by weight‐loss and electrochemical methods. A formulation consisting of 300ppm 2‐Cl EPA and 300ppm Zn²⁺ was observed to deliver 95 percent inhibition efficiency. A suitable mechanism of corrosion inhibition has been proposed which is based on the results obtained from polarization study and uv‐visible absorption and reflectance spectra. 2‐Cl EPA‐Zn²⁺ system appears to function as a mixed inhibitor. The protective film consisted of Fe²⁺ ‐2‐Cl EPA complex, Zn(OH)₂ and oxides of iron. The film was found to be semiconducting in nature.