The inhibition of the corrosion of mild steel in 1？M H2SO4 solution by the pharmaceutically active compound esomeprazole (ESP) has been investigated by using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements. The effect of temperature on the corrosion behavior with the addition of different concentrations of ESP was studied in the temperature range of 30–60°C. Results obtained revealed that the inhibition efficiency increased with the increase in concentration of the inhibitor but decreased with the increase in temperature. The addition of KI increased the inhibition of ESP to a considerable extent. The experimental results suggest that the presence of iodide ions in the solution stabilized the adsorption of the ESP molecule on the mild steel surface, thereby improving the inhibition efficiency. Polarization curves indicated that the ESP belonged to a mixed-type inhibitor. Adsorption of the inhibitor on the mild steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined. Surface analysis via scanning electron microscope (SEM) and atomic force microscope (AFM) shows a significant improvement in the surface morphology of the mild steel plate. 1. Introduction The environmental consequence of corrosion is enormous, and its inhibition has been deeply investigated. It has been found that one of the best methods of protecting metals against corrosion involves the use of inhibitors which are substances that slow down the rate of corrosion [1]. Therefore, the development of corrosion inhibitors based on organic compounds containing nitrogen, sulphur, and oxygen atoms is of growing interest in the field of corrosion and industry [2]. The corrosion inhibition is a surface process, which involves adsorption of the organic compounds on a metal surface. The adsorption depends mainly on the electronic structure of the molecule [3]. The inhibition efficiency of organic compounds depends on the mode of interaction with the metal surface and molecular structure. However, there is an increasing concern about the toxicity of most corrosion inhibitors. The toxic effects not only affect living organisms but also poison the environment [4]. Due to the toxicity of some corrosion inhibitors, there has been increasing search for green corrosion inhibitors. Inhibitors in this class are those that are environmentally friendly and nontoxic. Recently, several studies have been carried out on the inhibition of corrosion of metals by drugs.
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