Synthesis, Characterization, and DFT of Some Thiazole Derivatives as Carbon Steel Corrosion Inhibitors in 1 M HCl

By reacting 2-(1-(4-aminophenyl)ethylidene)hydrazine-1-carbothioamide (1) with various α-halocarbonyl compounds, such as 3-chloropentane-2,4-dione 2 and 1-chloro-1-((4-substituted phenyl)diazenyl)propan-2-one 4a-c, this work produces a new series of thiazole derivatives 3 and 5a-c. The new substituted thiazole derivatives 3, 5a, 5b, and 5c, were determined and examined for their ability to suppress mild steel corrosion in 1 M HCl using spectroscopic analyses. The findings showed that inhibition efficiency rose with concentration, peaking at 5 g/L (93%). The charge transfer resistance (R_ct) increased from 36 Ω cm² (blank) to 370.87 Ω cm²at 5 × 10^-3 M concentration. It was found to have an efficiency IE% in the order of 5c 95.10% > 5b 92.56% > 5a 89.01% > 3 83.41% at elevated temperatures (298 K for 5 × 10^-3 M concentration). While adsorption followed the Langmuir isotherm, itindicates the negative values of ΔGads which indicate a spontaneous adsorption process. The surface analysis results from SEM were consistent with previous experimental results. Moreover, compound 5c's energy gap (ΔE) = 1.99 eV and a larger value of E_HOMO, indicating substantial inhibitory activity. The most potent inhibitor was identified by DFT thiazole derivative 5c. These computations showed that a high corrosion prevention efficiency is a result of the thiazole derivative with group of high electron density.