Corrosion inhibition and adsorption properties of some manganese metal complexes on mild steel in sulfuric acid solutions

Metal complexes are frequently employed in industry as key compounds in medicinal chemistry. The interaction between metal complexes and metal surfaces is crucial in corrosion chemistry. Open circuit potential-time measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques are used to investigate the effects of two manganese metal complexes, Mn-2(PAB)(4)(Phen)(2) and Mn-2(PAB)(3)(Phen)(2)(OH) abbreviated as MnP4 and MnP3OH, on the corrosion of mild steel in sulfuric acid solutions. The chemical and structural characteristics of the complexes are confirmed using powder X-ray diffraction, thermal gravimetric analysis and FTIR. Both complexes act as potential corrosion inhibitors, with inhibition efficiencies of 90% at 10(-3) mol<middle dot>L-1. Potentiodynamic polarization curves suggest that MnP4 and MnP3OH are anodic type inhibitors. The impedance responses indicate that the corrosion process of mild steel is activation controlled. The obtained results revealed that the inhibition efficiency decreases with increasing temperature, which is suggestive of physical adsorption mechanism. The corrosion inhibition mechanism was further corroborated by the values of kinetic and thermodynamic parameters obtained from the experimental data.