The College of Education for Pure Sciences, Department of Chemistry, reviewed a master's thesis on "Preparation of Schiff Base Inhibitors and Studying Their Corrosion Reduction Effect." The thesis, submitted by researcher Hawraa Ali Abdul Wahid, included the preparation of five compounds derived from the aldehyde 2-hydroxy-1-naphthaldyde and the amines 4-aminophenol, 3-aminophenol, 2-aminophenol, 4-aminobenzenesulfonmide, and Benzidene. These compounds were characterized using infrared spectroscopy, proton nuclear magnetic resonance (H¹NMR), and mass spectrometry. The study involved using the compounds prepared from a series of Schiff bases as corrosion inhibitors for carbon steel alloys in an acidic medium of 1 M hydrochloric acid. The corrosion rate was measured using extrapolation of Tafel plots at different temperatures and concentrations. The results showed that all compounds inhibited corrosion by reducing the corrosion current density (Icorr) of C45 carbon steel in the presence of inhibitors compared to their absence. The corrosion rate was also found to be lower in the presence of inhibitors than in their absence. Specifically, the corrosion rate using inhibitor A was 0.546, the lowest value at a concentration of 0.05 M and a temperature of 298 K. The inhibition efficiency (IE%) increased with increasing inhibitor concentration at each temperature. Generally, the inhibition efficiency of all compounds decreased at 308 K and increased at 318 K, which explains the mixed behavior exhibited by the inhibitors at the same concentration. The percentage values ​​of the inhibition efficiency indicate that the inhibition efficiency of inhibitor A (90%) was the highest at a concentration of 0.05 M and a temperature of 318 K.

Several thermodynamic functions were also calculated, including activation energy (Ea), change in free energy (ΔG), change in enthalpy (ΔH), and change in entropy (ΔS). It was found that the adsorption of molecules onto the metal surface follows the Langmuir isotherm model, and that the adsorption process for corrosion inhibitors is of a mixed (chemical-physical) type.

This section also included the calculation of theoretical results using computational chemistry software to evaluate the efficiency of the prepared compounds as corrosion inhibitors for C54 carbon steel alloy. The results showed that compounds A and N (-5.242 eV and -4.948 eV, respectively) possess the highest EHOMO orbital energy values, which enhances the inhibition efficiency. Furthermore, compounds N and A (3.852 eV and 3.541 eV, respectively) exhibit lower ΔEgab energy gap values. Therefore, the inhibitor's reaction on the steel surface will be stronger compared to the other prepared compounds, contributing to increased inhibition efficiency. Compounds A and N (1.771 and 1.926, respectively) are classified as soft bases due to their low hardness and high softness (0.565 and 0.519, respectively). Consequently, compounds A and N offer better inhibition performance than other inhibitors (C, E, and G), which are characterized by higher hardness and lower softness values. It was also observed that the increased number of transferred electrons (ΔN) in compounds A and N (0.956 and 1.08, respectively) contributed to increased inhibition efficiency, leading to their superiority over the other compounds in terms of inhibition efficiency, based on the analysis of Mulliken charge values. For the prepared and studied compounds, we find that compound A has the best adsorption sites compared to the other compounds

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