Abstract
In this work, a new inhibitor, triazole modified chitosan, was synthesized for the first time following chemical modification of chitosan using 4-amino-5-methyl-1,2,4-triazole-3-thiol. The newly synthesized biopolymer (CS–AMT) was characterized using FTIR and NMR, and then it was evaluated as an inhibitor against corrosion of carbon steel in 1 M hydrochloric acid. The corrosion testing and evaluation were performed thoroughly employing the weight loss method, electrochemical measurements and surface analysis. A maximum corrosion inhibition efficiency of >95% was obtained at 200 mg L−1 concentration of inhibitor. The adsorption of inhibitor obeyed the Langmuir isotherm and showed physical and chemical adsorption. The electrochemical study via impedance analysis supported the adsorption of the inhibitor on the surface of carbon steel, and the potentiodynamic polarization indicated a mixed type of inhibitor behavior with cathodic predominance. To get a better insight on the interaction of inhibitor molecules with the metal surface, a detailed theoretical study was performed using DFT calculations, Fukui indices analysis and molecular dynamics (MD) simulation. The DFT study showed a lower energy gap of CS–AMT and the MD simulations showed an increased binding energy of CS–AMT compared to the parent chitosan and triazole moieties thereby supporting the experimental findings.
Highlights
IntroductionThe polymeric molecules having a high molecular weight and a greater surface coverage have proved to be promising corrosion inhibitors
Carbon steel is widely used in the petroleum industries due to its cost-effectiveness and high mechanical strength
The effect of the different concentrations of CS–AMT on the inhibition performance was analyzed using the weight loss studies conducted in 1 M HCl by introducing the varying concentrations of CS–AMT from 50 mg LÀ1 to 250 mg LÀ1 to the test solution
Summary
The polymeric molecules having a high molecular weight and a greater surface coverage have proved to be promising corrosion inhibitors. Carboxymethyl cellulose, Tapioca Starch, Gum Arabic and Chitosan have been reported as promising corrosion inhibitors.[9,10,11] Chitosan is a polysaccharide bearing b-(1-4)-linked Nacetyl-D-glucosamine units in the chain. In the present work, it was considered worthwhile to test the newly synthesized chitosan–AMT (CS– AMT) to study the corrosion inhibition performance of carbon steel in 1 M HCl solution by weight loss and electrochemical measurements as well as surface analysis. Quantum chemical calculations using density functional theory (DFT) and Fukui analysis were performed to estimate the reactivity parameters of the inhibitor theoretically
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