Effect of Mercapto and Methyl Groups on the Efficiency of Imidazole and Benzimidazole-based Inhibitors of Iron Corrosion.

Ingrid Milošev,Nataša Kovačević,Anton Kokalj

doi:10.17344/acsi.2016.2326

Abstract

We report on the combined experimental and computational study of imidazole- and benzimidazole-based corrosion inhibitors containing methyl and/or mercapto groups. Electrochemical measurements and long-term immersion tests were performed on iron in NaCl solution, whilst computational study explicitly addresses the molecular level details of the bonding on iron surface by means of density functional theory calculations (DFT). Experimental data were the basis for the determination of inhibition efficiency and mechanism. Methyl group combined with mercapto group has a beneficial effect on corrosion inhibition at all inhibitor concentrations. The beneficial effect of mercapto group combined with benzene group is not so pronounced as when combined with methyl group. The latter is in stark contrast with the behaviour found previously on copper, where the effect of methyl group was detrimental and that of mercapto and benzene beneficial. Explicit DFT calculations reveal that methyl-group has a small effect on the inhibitor-surface interaction. In contrast, the presence of mercapto group involves the strong S-surface bonding and consequently the adsorption of inhibitors with mercapto group is found to be more exothermic.

Highlights

The inhibition of corrosion using corrosion inhibitors has been for decades one of the most important method of corrosion protection
The effect of mercapto and methyl groups on the adsorption bonding of imidazole and benzimidazole based inhibitors on Fe(110) surface and their efficiency of iron corrosion in 3 wt.% NaCl solution was studied by means of explicit density functional theory calculations (DFT) calculations and corrosion experiments, respectively
In contrast to copper, where mercapto containing derivatives of imidazoles were beneficial for all concentrations tested, their inhibition of iron corrosion was advantageous compared to other derivatives only at low inhibitor concentration

Summary

Introduction

The inhibition of corrosion using corrosion inhibitors has been for decades one of the most important method of corrosion protection. In this study we test the applicability of several imidazole-type molecules as corrosion inhibitors for iron in NaCl solution. At 1 mM concentration the order of inhibition efficiency, IE, is: ImiMe < ImiH < BimH < SH-ImiMe < SH-BimH. The mercapto group and benzene group were shown to have a beneficial effect on corrosion inhibition, Milo{ev et al.: Effect of Mercapto and Methyl Groups on the Efficiency

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Conclusion