Inhibitive Effect by Acid Extracts of Malachra capitata Leaves on the Sulphuric Acid Corrosion of Mild Steel

Extract of Malachra capitata leaves was investigated as corrosion inhibitor of mild steel in 1 N H₂SO₄ using conventional weight loss, electrochemical polarizations, electrochemical impedance spectroscopy and scanning electron microscopic studies. The weight loss results showed that the extract of Malachra capitata leaves is an excellent corrosion inhibitor, electrochemical polarizations data revealed the mixed mode of inhibition and the results of electrochemical impedance spectroscopy have shown that the change in the impedance parameters, charge transfer resistance and double layer capacitance, with the change in concentration of the extract is due to the adsorption of active molecules leading to the formation of a protective layer on the surface of mild steel. Scanning electron microscopic studies provided the confirmatory evidence of improved surface condition, due to the adsorption, for the corrosion protection.