Performance and Mechanism of Alkylimidazolium Ionic Liquids as Corrosion Inhibitors for Copper in Sulfuric Acid Solution.

Guocai Tian,Kaitao Yuan

doi:10.3390/molecules26164910

Guocai Tian, Kaitao Yuan

Open Access

https://doi.org/10.3390/molecules26164910

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Abstract

The addition of corrosion inhibitors is an economic and environmental protection method to prevent the corrosion of copper. The adsorption, performance, and mechanism of three 1-alkyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO4, [HMIM]HSO4, and [OMIM]HSO4) ionic liquids (ILs) on the copper surface in 0.5 M H2SO4 solutions were studied by quantum chemical calculation, quantitative structure-activity relationship (QSAR), and molecular dynamics simulation. It is found that the main reactive site is located on the imidazolium ring (especially the C2, N4, and N7 groups). When the alkyl chain of the imidazolium ring is increasing, the molecular reactivity of the ILs and the interaction between the ILs inhibitor and copper surface are enhanced. The imidazole ring of the ILs tends to be adsorbed on Cu (111) surface in parallel through physical adsorption. The order of adsorption energy is [Bmim]HSO4 < [Hmim]HSO4 < [OMIM]HSO4, which is in agreement with the experimental order of corrosion efficiency. On the imidazole ring, the interaction between the copper surface and the C atom is greater than that between the copper surface and the N atom. It is found that ILs addition can hinder the diffusion of corrosion particles, reduce the number density of corrosion particles and slow down the corrosion rate. The order of inhibition ability of three ILs is [Bmim]HSO4 < [Hmim]HSO4 < [OMIM]HSO4,which agree well with experimental results. A reliable QSAR correlation between the inhibition corrosion efficiency and molecular reactivity parameters of the ILs was established.

Highlights

Copper and its alloys are widely utilized as an important material in various industrial applications such as microelectronic, military, and civilian living life owing to its electrical conductivity, good thermal properties, mechanical workability, good availability, cheap, and corrosion resistance properties
Based on the discussion above, it can be concluded that imidazolium molecules, which had a number of increase in chain length of the imidazolium ring increases the distribution of ƒ+ and ƒ−, making it easier for ionic liquids (ILs) to give or accept electrons, which is in agreement with the experimental prediction that the adsorption is more pronounced with an increase in the carbon chain length of the alkyl connecting with the N of imidazolium ring due to their of 17 electron-releasing ability
Global reactivity parameters reveal that the variety of these parameters are with the difference of electrons transferred ability and molecular reactivity, and the adsorption ability from low to high is [BMIM]HSO4 < [HMIM]HSO4 < [OMIM]HSO4

Summary

Introduction

Copper and its alloys are widely utilized as an important material in various industrial applications such as microelectronic, military, and civilian living life owing to its electrical conductivity, good thermal properties, mechanical workability, good availability, cheap, and corrosion resistance properties. The common ways for corrosion prevention are isolation protection, electrochemical protection, and adding inhibitors. One effective and useful approach to protect copper metals against the corrosion problem of acid solutions is adding corrosion inhibitors, which are often ionic liquids because they have many special properties such as better thermal stability, good solubility, high conductivity, wider electrochemical window, and so on [5,7,12,13]. Some ionic liquids (ILs) based on imidazolium, pyridinium, and benzotriazole have been used as corrosion inhibitors for copper and its alloys in acid solution and achieved good results. Ionic liquids are popularly used as sustainable and green corrosion inhibitors for metal [5,7,12,15,16,17,18]. Many researchers used electrochemical tests and surface investigations to obtain the inhibition efficiency and found that the adsorption cal tests and surface investigations to obtain the inhibition efficiency and found that the adsorption process of an inhibitor can be described by Langmuir adsorption [19,20]

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