Novel Compounds of Imidazole Derivatives as Effective Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution: Electrochemical and Spectroscopic Characterization

1. Introduction

Metal corrosion is an unavoidable difficulty for industries. Mild steel is the most extensively employed metal in industrial applications because of its excellent mechanical characteristics and inexpensiveness, (Verma, 2015a). A Large quantity of the mild steel, as well as other iron alloys, is destroyed by corrosion in aggressive media, especially in acid environments which cost billions of dollars every year (Verma, 2015b). This situation has grown to be a more important task for corrosion engineers and the scientific neighborhood. From an economic point of view, stopping or slowing down this deterioration has become obligatory. The only solution to this undesirable problem is to use corrosion safety methods. Corrosion inhibitors are commonly added to the aggressive acids to prevent the severe metal dissolution during acid treatment (Tawfik, 2015). Therefore, specific amounts of various synthetic corrosion inhibitors are added to the HCl solution for mild steel corrosion control. Recently, imidazole derivatives compounds have gained significant attention in corrosion science (Ouakki, 2019, 2018; Rbaa, 2017a; Galai, 2016). Literature reviews reveal that heterocyclic compounds based on imidazole are used as efficient corrosion inhibitors for metals in an acid medium (Yadav, 2016; Zhang, 2015)

Most organic compounds inhibit corrosion via adsorption on the metal surface. This adsorption mainly depends on some physico-chemical properties of the molecule, related to its functional groups (e.g. nitrogen, oxygen and sulfur atoms), aromaticity, the possible steric effects and electronic density. The aim of this work is to study the inhibition properties of two imidazole derivatives on mild steel corrosion in 1M HCl using gravimetric measurements, potentiodynamic polarization curves, and electrochemical impedance spectroscopy. It also aims to predict the thermodynamic feasibility of these compounds on the steel surface. In addition, detailed investigation of temperature were also carried and discussed to improve a better understanding of the adsorption mechanism of the studied inhibitors. The surface of the mild steel upstream and downstream of corrosion was characterized by SEM-EDAX, and the gravimetric solution was analyzed by UV–visible spectrometry. The corrosion inhibition performance of the compound IM-Cl is significant compared with that of the compound IM-CH₃ and this is explained by the existence of a mesomeric electron donor group (-Cl) carried by IM-Cl improving thus its adsorption capacity on the metal (Rbaa, 2017b, 2017c).