Abstract
In this book chapter, the authors focus on the comparative study of some benzimidazole-substituted compounds used as corrosion inhibitors for mild steel in molar Hydrochloric acid solution. It has been determined that the quinazolinone studied compounds exhibit a very good performance as corrosion inhibitors for mild steel in molar Hydrochloric acid solution, as the halogen-substituted compounds show better inhibitive performance than the non-halogen-substituted one. Correspondence between inhibition property, molecular structure, and halogen substitution of benzimidazole-substituted compounds is investigated, using chemical, electrochemical, and theoretical methods. Halogen substitution effect on the inhibition performance has also been explored by quantum chemical computations and obvious correlations were observed. The binding energies of tested compounds on Fe(110) surfaces were calculated using Monte Carlo simulation. Bromide-substituted compound shows better inhibitive performance than the chloride-substituted one.
TopIntroduction
Metals and their alloys offer excellent mechanical properties, such as high specific strength and good ductility. Metals is applied to approximately the entire industrial field for the reason of its excellent properties. However, its corrosion usually results in enormous financial losses and potential security problems where the protection technology has attracted the interest of several researchers and industrials.
Corrosion studies have attracted considerable interest in the areas of materials chemistry and industrial chemistry. Corrosion is the undesirable process that is the progressive destruction of materials by chemical reaction with their environment. This chemical process can also be expressed as electrochemical oxidation of metals in reaction with an oxidant such as oxygen (El Kacimi et al., 2020). Hydrochloric acid pickling bath is used to remove the corrosion products from the metal working. Over-pickling can cause a serious damage and physical properties of metals structure can be easily done (Rbaa et al., 2017; Trabanelli et al., 1991; Sastri et al., 1997; Alaoui et al., 2020). At present, the addition of inhibitors is one of the most convenient and practical methods of protecting metal against corrosion in acidic media. Among the various kinds of inhibitors, the organic corrosion inhibitors, especially the compounds with the aromatic ring or heteroatoms, are economic and easy to prepare, therefore, they are regarded as the most promising tools to resolve the industrial issues (Mora-Mendoza et al., 2002; Schmitt et al., 1984; Alaoui et al., 2018).
Perusal of our previous work reveals that two benzimidazoles derivatives Q-H and Q-Cl have been synthesized and its chemical structure was elucidated and confirmed using different spectral methods such as 1H and 13C NMR spectroscopy. Their inhibitive action against the corrosion of mild steel in 1.0 M hydrochloric acid solution were investigated at different temperatures in the range from 298 to 328±2 K by a series of known techniques such weight loss and electrochemical measurements. It was found that the studied compounds exhibit a very good performance as inhibitors for mild steel corrosion in 1.0 M HCl. Results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitor’s. It has been determined that the adsorption for the studied inhibitors on mild steel complies with the Langmuir adsorption isotherm at all studied temperatures (El Azhar et al., 2001). Since there is no explanation and/or published research evaluating the effect of halogen atoms on the corrosion inhibition properties of benzimidazole-substituted compounds.
Key Terms in this Chapter
Chemical electronegativity: This is the tendency for an atom of a given chemical element to attract shared electrons or electron density when forming a chemical bond.
Corrosion inhibitor: This is a chemical substance that when present in the corrosion system at a suitable concentration decreases the corrosion rate, without significantly changing the concentration of any corrosive agent.
Molecular dynamics (MD): This is a computer simulation method for analyzing the physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a fixed period, giving a view of the dynamic evolution of the system.
Potentiodynamic polarization: This is a technique where the potential of the electrode is varied at a selected rate by application of a current through the electrolyte.
Density-functional theory (DFT): This is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure or nuclear structure, principally the ground state of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals. In the case of DFT, these are functionals of the spatially dependent electron density.
Electrochemical Impedance Spectroscopy (EIS): This is one of the most important electrochemical techniques where the impedance in a circuit is measured by ohms (as resistance unit).
Monte Carlo Methods: These are a broad class of computational algorithms that rely on repeated random sampling to obtain numerical results. The underlying concept is to use randomness to solve problems that might be deterministic in principle. They are often used in physical and mathematical problems and are most useful when it is difficult or impossible to use other approaches. Monte Carlo methods are mainly used in optimization, numerical integration, and generating draws from a probability distribution.
Corrosion rate: This is the speed at which any metal in a specific environment deteriorates. It also can be defined as the amount of corrosion loss per year in thickness.