Oleo-chemicals triazoles as effective corrosion inhibitors for mild steel in acetic acid media

Corrosion poses a very serious problem to industries and mankind, affecting both the cost and productivity. Corrosion inhibitors are one of the most promising methods to combat corrosion. The use of ecofriendly corrosion inhibitors are increasing day by day. Oleo chemicals are derivatives of the component of vegetable, animal and mineral oils. Oleo chemicals constitute an important and potential class of corrosion inhibitors. Organic acids are slightly reducing and can be relatively corrosive. Selected oxadiazoles of fatty acids of lauric acid, oleic acid and undecenoic acid - namely 3-heptadecene-4-aryl-5-mercapto-1, 2, 4-triazole (HAMT); 3-undecane-4-aryl-5-mercapto-1, 2, 4-triazole (UAMT); and 3-decene-4-aryl-5-mercapto-1, 2, 4-triazole (DAMT) - were synthesized. Their influence on the inhibition of corrosion of mild steel in 20% acetic acid (CH3COOH) was investigated by weight loss and potentiodynamic polarization techniques. The inhibition efficiency of the compounds was found to vary with concentration, immersion time and temperature. All the compounds showed good inhibition efficiency (IE) in acetic acid solution. Thermodynamic parameters such as E_a, ΔH, ΔS, ΔG and Q were also calculated to investigate the mechanism of inhibition. All the investigations suggested that the compound follows the Langmuir adsorption isotherm. The negative values of G_ads indicate the spontaneous adsorption of inhibitors on the mild steel surface. Potentiodynamic polarization study revealed that all three inhibitors, HAMT, UAMT, and DAMT are mixed inhibitors. Electrochemical impedance spectroscopy was also used to investigate the inhibition mechanism.