This research aimed to develop a better understanding of the corrosion inhibition of the mild steel in acidic medium by new organic molecules. For this purpose, two new compounds namely, 2,3-dihydrobenzo[4,5]imidazo[2,1-b]thiazole (2-BIT) and 3,4-dihydro-2H-benzo[4,5]imidazo[2,1-b]thiazole (3-BIT) were synthesized and evaluated for mild steel (MS) corrosion in HCl. Analyses were carried out using weight loss measurements, electrochemical techniques, and scanning electron microscope (SEM). The adsorption of inhibitors onto the steel surface follows the Langmuir adsorption model. Generally, results showed that the corrosion inhibition efficiency of the investigated molecules was found to increase with increased concentration of inhibitors. Electrochemical tests, i.e., electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques, showed that the addition of our investigated inhibitors decreases the dissolution of the metal and generally act as mixed-type inhibitors. In addition, the influence of temperature (from 303 to 333 K) on the corrosion inhibition was studied, and the results demonstrated that with an increase in temperature, the inhibition efficiency decrease. SEM results confirmed that the inhibition process is due to a protective film that prevents corrosion. Similarly, the results showed that the inhibitory efficiencies reach 93% at 5 × 10⁻³ M in the case of inhibitor 3-BIT. These results revealed that this compound could effectively control and reduce the corrosion rate of mild steel in the corrosion test solution.

In this work, we investigated the addition effect of two organic compounds namely; p‐anisidine (P1) and 4‐nitroaniline (P2) against corrosion of C38 steel in an acidic medium HCl 1 M. We opted for these inhibitors belonging to the aniline family which is characterized by their solubility, their low cost, and their use as corrosion inhibitors in acidic environments. The concentration effect of the two products P1 and P2 either by stationary or by transiency measurements appears a significant decrease in the corrosion rate, and that the inhibition efficiency IE% reaches a value of 88.55 % and 84 % for a concentration of 1 mM respectively of P1 and P2. The thermodynamic parameters taken from the electrochemical impedance curves indicate that the tested inhibitors are adsorbed on the metal surface by a mixed mechanism (physical‐chemisorption), because the free adsorption energy of P1 and P2 is respectively equal to −38.02 Kj.mol ⁻¹ and −37.56 Kj.mol ⁻¹ , and they are subjected to the Langmuir isotherm. The temperature effect lets to determine the activation energy (E _a ) from the Arrhenius equation; however, the values of E _a indicate the adsorption of organic compounds on the metal surface. Scanning electron microscopy (SEM) suggested that the products tested could effectively block acid attack on metal surfaces. In parallel to experimental approach, theoretical one based on theoretical function density (DFT) calculation and Monte Carlo (MC) simulation is considered to investigate in depth the inhibition behavior of studied compounds.