Anticorrosion studies of some hydantoin derivatives for mild steel in 0.5 M HCl solution: Experimental, quantum chemical, Monte Carlo simulations and QSAR studies

Highlights

• Some hydantoin derivatives were investigated for their corrosion inhibition potentials.

• The corrosion test was based on mild steel in 0.5 M HCl.

• EIS, potentiodynamic polarization methods, Monte Carlo simulation were used for the study.

• These inhibitors were adsorbed onto surfaces obeying Langmuir adsorption model.

• Theoretical and experimental results were in agreement.

Abstract

Some hydantoin derivatives namely, 1-methylhydantoin (MHYD), 5,5-dimethyl-hydantoin (DMHYD), hydantoin-5-acetic acid (HYDAC), 1,3-dibromo-5,5-dimethylhydantoin (DBDMHYD), 5-methyl-5-phenylhydantoin (MPHYD), and hydantoin (HYD) were studied as corrosion inhibitors for mild steel in 0.5 M HCl using experimental and theoretical methods. Tafel polarization measurements showed that the hydantoin derivatives are mixed type inhibitors and obeyed the Langmuir adsorption isotherm model. Scanning electron microscopy (SEM) analyses of surface morphology suggested that the hydantoin derivatives protect mild steel surface in 0.5 M HCl. Quantum chemical calculations and molecular dynamic simulations results were in good agreement with the experimental results. Quantitative structure activity relationship studies showed that the inhibitive performances of the studied compounds correlated well with their molecular weights, frontier molecular orbitals energy gap, fraction of electron transferred and binding energy.

Introduction

Corrosion is a major problem that confronts many industries. A large percentage of total production costs in oil and gas industries are usually channelled towards repression of corrosion problems [1]. The use of corrosion inhibitors has been described as one of the most popular, convenient and cost-effective methods of controlling metal corrosion in aqueous environments [2], [3], [4], [5], [6]. Mild steel is a widely used alloy of iron with applications in various industries where aqueous solutions, mostly acids, are inescapably utilized for different beneficial purposes [7]. For this reason, corrosion of mild steel in acidic media especially with regard to the use of corrosion inhibitors is a dominant research in corrosion science.

Generally, organic compounds with π-electron functional groups and/or heteroatoms such as N, O, S, and P are regarded as potential corrosion inhibitors [8], [9], [10], [11], [12], [13], [14], [15], [16]. However, the use of many of these compounds is restricted by several factors, particularly environmental malignancy. Modern global demands for environmental awareness and new environmental protection regulations have necessitated the use of environmentally benign substances as corrosion inhibitors [17]. For this reason, recent research activities have focused on designing and investigating environmental friendly materials as corrosion inhibitors. Several natural [17], [18], [19], [20], [21], [22], [23], [24] and synthetic [17], [25], [26], [27], [28], [29], [30], [31], [32], [33] organic compounds have shown appreciable performances in inhibiting mild steel corrosion in acidic environments.

Designing non-toxic corrosion inhibitors has witnessed tremendous advancements with the use of biologically active and drug-based compounds as corrosion inhibitors [17], [34], [35], [36], [37], [38], [39], [40]. Gece [41] recently made a review of popular drugs that have been investigated as potential eco-friendly corrosion inhibitors. One family of drug-based compounds that has not been widely studied for their corrosion inhibition potentials is the hydantoin derivatives. These compounds are known for their non-toxicity, biological activities, and pharmaceutical applications [42], [43], [44], [45]. Hydantoin derivatives have also been found to exhibit corrosion inhibition activities [46], [47], [48], [49], [50].

However, studies on corrosion inhibition properties of hydantoins are still considered fragmentary as compared to other potentially non-toxic synthetic organic compounds. Those that report robust experimental and theoretical findings on inhibitive properties of these compounds on metal corrosion in acidic medium are particularly scanty. Al-Sawaad et al. [50] investigated the inhibitive effects of dimethylol-5-methylhydantoin (MHD) and its derivatives on corrosion of carbon steel N-80 in cooling water and found that up to 98% inhibition efficiency could be achieved for MHD at 50 mg/l and 303 K. Some substituted phenylhydantoin, thiohydantoin, and dithiohydantoin had been reported to exhibit mixed type corrosion inhibition activities for iron in 2 M nitric acid and 2 M sulphuric acid solutions [49]. In their findings, Madkour et al. [49] observed that the overall ranges of percentage inhibition efficiencies evaluated from polarization measurements for the seven tested hydantoin derivatives were 68.3–93.8% in HNO₃ and 81.4–91.0% in H₂SO₄ at 303 K.

Also, Yüce et al. [47] investigated the corrosion inhibition effect of 5,5 diphenyl 2-thiohydantoin on mild steel in 0.1 M HCl solution and found that the compound inhibit both anodic and cathodic reactions with maximum inhibition efficiency of 95% at 298 K. In another study, Yüce and Kardaş [46] showed that 2-thiohydantoin is an efficient mixed type corrosion inhibitor for mild steel in 0.1 M HCl.

The present study reports the corrosion inhibition properties of hydantoin (HYD) and its simple derivatives namely, 1-methylhydantoin (MHYD), 5,5-dimethyl-hydantoin (DMHYD), hydantoin-5-acetic acid (HYDAC), 1,3-dibromo-5,5-dimethylhydantoin (DBDMHYD) and 5-methyl-5-phenylhydantoin (MPHYD) for mild steel in 0.5 M hydrochloric acid medium. The 2D molecular structures of the compounds are shown in Fig. 1. Experimental findings were carried out using electrochemical techniques, that is, Tafel polarization and electrochemical impedance spectroscopy (EIS). Extensive theoretical quantum chemical calculations and molecular dynamic simulations studies were carried out to corroborate experimental results. Quantitative structure activity relationship (QSAR) studies were carried out to investigate the level of correlations between experimental inhibition efficiencies and molecular quantum chemical descriptors. To the best of our knowledge, the set of hydantoin derivatives investigated in the present work had not been tested for their corrosion inhibition potentials on mild steel in 0.5 M HCl in any previous work.