Theoretical and experimental investigation for mild steel in acidic environment using isoxazole sulfonamide derivatives as anticorrosion inhibitors

Two isoxazoles sulfonamides namely N-butyl-2-(N-((3-(p-tolyl)isoxazol-5-yl)methyl)sulfamoyl)benzamide (IS-Cl) and N-butyl-2-(N-((3-(4-chlorophenyl)isoxazol-5-yl)methyl)sulfamoyl)benzamide (IS-CH₃) were evaluated as some corrosion inhibitors for mild steel (MS) in 1 M HCl environment. Different experimental techniques including EFM, PDP, EIS, SEM, and EDS were investigated to understand the anticorrosion properties. Furthermore, DFT, PDOS, and MDS approaches were utilized to explore the correlation between isoxazoles sulfonamides and corrosion inhibitors effectiveness. PDP measurements revealed that isoxazoles function as mixed inhibitors through adsorption on the MS samples surface. Corrosion inhibition efficiency of PDP at 10⁻³M of IS-Cl (97 %) is higher than that of the IS-CH₃ (94.9 %). The chemical adsorption process of isoxazoles sulfonamide heterocyclics were found to conform the Langmuir adsorption isotherm. Results of PDOS for the adsorption molecules onto the Fe(110) iron was used to understand and explain the inhibition mechanism.