Inhibition Effect of Essential Oil Extracts on the Corrosion Inhibition of Mild Steel in Chloride–Sulphate Media

Abstract

Studies on corrosion inhibition effect of the combined admixture of sage and lavender oil extracts on mild steel in dilute H2SO4 and HCl solutions were performed to assess their optimum inhibition efficiency at low concentrations through potentiodynamic polarization technique, weight loss analysis and optical image analysis. The surface of the control steel specimen in H2SO4 was subject to severe degradation, while the steel surface from HCl selectively deteriorated with visible corrosion pits. The oil extracts effectively inhibited mild steel corrosion in both acids with optimal inhibition efficiency of 86.92 and 96.90% in H2SO4, and 84.68 and 97.59% in HCl from potentiodynamic polarization and weight loss analysis. Anodic inhibition behavior was the dominant inhibition mechanism in H2SO4 resulting from molecular coverage of the steel, and cathodic inhibition mechanism dominated in HCl solution. Thermodynamic calculations showed the extract molecules performed through chemisorption adsorption mechanism according to Langmuir, Frumkin and Freundlich isotherms.