Anticorrosive efficacy and adsorptive study of guar gum with mild steel in acidic medium

Background: Gums have been found to be good corrosion inhibitors due to their functional group; they form complexes with metal ions and on the metal surfaces. Most gums have -COOH functional groups, which can increase the contribution of electron or charge transfer and hence facilitate inhibition through adsorption. Methods: The corrosion and inhibition behaviors of mild steel in hydrochloric, sulphuric, and nitric acid in the presence of Cyamopsis tetragonoloba (guar gum) have been studied using the weight loss, gas chromatography mass spectrometry (GC-MS), and thermometric techniques. Results: The temperature studies reflect that the percentage of inhibition efficiency is decreased with increase in temperature and that indicates the mechanism of physical adsorption. The calculated values of activation energy (Ea) also support the physiosorption process. The thermodynamic parameters such as heat of adsorption (Qads) and free energy of adsorption (ΔGads) suggested that the adsorption of inhibitor on the mild steel surface is exothermic and followed by spontaneous process. Conclusions: The formation of an adsorbed protective film of the inhibitor molecules on the mild steel surface is confirmed by scanning electron micrographs (SEM), which proves that the guar gum acts as good inhibitor at 1N acids concentration.