Corrosion inhibition properties of the combined admixture of essential oil extracts on mild steel in the presence of SO42− anions

The combined admixture of essential oil extracts, salvia officinalis and simmondsia chinensis was studied at low concentrations to assess their corrosion inhibition performance on mild steel in 1 M H2SO4 solution. Electrochemical studies were performed with potentiodynamic polarization test and weight loss analysis while open circuit potential measurement was employed to assess the thermodynamic stability of the corrosion properties of the compound with respect to time. Results obtained showed optimal inhibition efficiency of 86.58% and 83.29% at 6% and 5% volumetric concentration from the electrochemical test. The corrosion potential of the inhibited steel displaced significantly in the positive direction compared to the significant negative displacement of corroded steel due to surface coverage from the inhibitor molecules on the inhibited steel. Thermodynamic calculations showed chemisorption adsorption mechanism according to Langmuir, Frumkin and Freundlich adsorption isotherm models. Optical images of inhibited mild steel surface significantly contrast the corroded non-inhibited steel which showed the presence of surface oxides, general deterioration and macro pits. Keywords: Corrosion, Mild steel, Inhibition, Adsorptio