Electrochemical Investigation of 4-Hydroxy n-[2-Methoxy Naphthalene Methylidene] Benzohydrazide as Corrosion Inhibitor of Mild Steel in Acidic Medium

The corrosion rate of mild steel in hydrochloric acid and in sulphuric acid was determined by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.5 M concentrations of HCl and of H₂SO₄ using 4-hydroxy n-[2-methoxy naphthalene methylidene] benzohydrazide (HNBH) as an inhibitor The inhibition efficiency of HNBH for the corrosion mitigation of mild steel was studied by varying the concentration of the inhibitor and temperature. It was found that the inhibition efficiency of HNBH increased with increase in the inhibitor concentration in both media. The maximum of 80% inhibition efficiency at the optimum inhibitor concentration of 2.5 × 10^–4 M was achieved. However, with an increase in temperature, the inhibition efficiency decreased. The corrosion inhibition by HNBH took place through physisorption. The adsorption isotherm fitting with the experimental data was identified to find out the mechanism of inhibition. The results indicated that HNBH functions as mixed type inhibitor and follows the Langmuir adsorption isotherm. The surface of the specimen was analyzed using scanning electron microscopy.