Inhibition of corrosion of mild steel in 1 M HCl by the essential oil or solvent extracts of Ptychotis verticillata

The essential oil and solvents extract of Ptychotis verticillata have been tested as inhibitors of corrosion of mild steel in 1 M HCl. Measurement of weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization curves were used to evaluate inhibition of corrosion in 1 M HCl. The efficiency of inhibition was found to increase with increasing inhibitor concentration, because of adsorption of inhibitor molecules on the metal surface; adsorption was in accordance with the Langmuir isotherm. In 1 M HCl the efficiency of inhibition was 74.6 % for 1.08 g/L essential oil rich in phenolic compounds as major compounds (48 %). Efficiency of inhibition, as determined by measurement of weight loss, was 75 and 86 %, respectively, for diethyl ether and ethyl acetate extracts at 0.5 g/L.