Inhibitory action of Albizia zygia gum on mild steel corrosion in acid medium

Abstract

The corrosion and inhibition behaviours of mild steel in sulphuric acid in the presence of Albizia zygia gum (AZ) have been studied using the weight loss, gasometric, Fourier transform infrared (FTIR) and thermometric techniques. The temperature studies reflect that the percentage of inhibition efficiency is decreased with rise in temperature and that indicates the mechanism of physical adsorption. The calculated values of activation energy (Ea) also support the physisorption process. The thermodynamic parameters such as heat of adsorption (Qads) and free energy of adsorption (ΔGads) are suggested that the adsorption of inhibitor on the mild steel surface is exothermic and followed by spontaneous process. The adsorption of the inhibitor on mild steel surface involves the formation of multimolecular layer through C-H bending vibrations due to alkenes at 703.08 and 933.58.01 cm-1, C-O stretches due to carboxylic acid, ester, ether and alcohol at 1084.03 and 1150.58 cm-1, C-O stretch due to ketone /aldehyde/carboxylic acid at 1826.65 cm-1, C-H aliphatic stretch at 2820.99 cm-1 and C-H stretch at 3026.41.79 cm-1, which support physical adsorption. The observed results indicate that A. zygia gum could serve as an effective inhibitor on mild steel in sulphuric acid. Key words: Albizia zygia gum, thermodynamics, mild steel, sulphuric acid, adsorption.