Corrosion inhibition study of iron in sulphuric acid 1M by hexa methylene diamine tetra methyl-phosphonic acid

The efficiency of hexa methylene diamine tetra methyl-phosphonic acid (HMDTMP), as corrosion inhibitor for iron in 1M H2SO4, has been determined by gravimetric and electrochemical measurements. Polarization curves indicate that the compound is mixed inhibitor, affecting both cathodic and anodic corrosion currents. Adsorption of HMDTMP derivatives on iron surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy value confirms the chemical nature of the adsorption. EIS results show that the change in the impedance parameters (Rt and Cdl) with concentration of HMDTMP is indicative. The adsorption of this molecule leads to the formation of a protective layer on iron surface.