Hibiscus cannabinus extract as a potential green inhibitor for corrosion of mild steel in 0.5 M H2SO4 solution

The inhibitory effect of extract of Hibiscus cannabinus on corrosion of mild steel in aqueous 0.5 M H2SO4 was investigated by weight loss method, potentiodynamics polarisation technique and electrochemical impedance spectroscopy (EIS). The inhibition efficiency of Hibiscus cannabinus extract on corrosion of mild steel in 0.5 M H2SO4 solution increases on increasing in concentration of the extract and decreases with rise in temperature. Potentiodynamic Polarization measurement indicates that Hibiscus cannabinus acts as a mixed-type inhibitor. The increase in activation energy of corrosion process in the presence of the extract indicates that the extract retards the rate of corrosion of mild steel in 0.5 M H2SO4 solution. The nature of adsorption of the extract on mild steel surface is found to obey Langmuir adsorption isotherm. EIS measurement result is also correlated with the result of polarization. SEM study confirmed the adsorption of inhibitor molecules on mild steel surface.