A detailed experimental and theoretical evaluations of two thiazolidine-2, 4-dione derivatives as corrosion inhibitors for carbon steel in a hydrochloric acid electrolyte

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In this study, we conducted a comparative analysis of the inhibiting effect of two recently developed thiazolidine-2,4-dione derivatives, namely (Z)-3-allyl-5-(4-bromobenzylidene) thiazolidine-2,4-dione (TZD1) and (Z)-5-(4-bromobenzylidene) thiazolidine-2,4-dione (TZD2), on the corrosion protection of carbon steel (Csteel) in a 1 M HCl electrolyte. Both potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques were used to do this comparison. The results indicate that the concentrations of TZD1 and TZD2, as well as the experimental temperature, are important factors that affect inhibitory efficacy. At 303 K and a concentration of 10−3M, the highest significant inhibition rates were achieved, reaching 93.7% for TZD1 and 91.7% for TZD2. The PDP analysis revealed that TZD1 and TZD2 are mixed-type inhibitors that primarily function as anodic inhibitors. Using the Langmuir isotherm model as a guide, TZD1 and TZD2 molecules chemisorb onto the steel surface. Surface characterization analysis utilizing scanning electron microscopy (SEM), contact angle (CA), and X-ray diffraction (XRD) confirmed this interaction. Additionally, UV-visible spectra showed that TZD1 and TZD2 molecules interact significantly with Fe ions at certain atomic positions. To investigate how the molecular structure of TZD1 and TZD2 affects their ability to inhibit corrosion, Fukui functions, Molecular Dynamics Simulations (MDS), and DFT calculations were employed. An examination was also conducted to determine how the thiazolidine derivatives protonate in an acidic environment. Strong agreement was observed between the outcomes of these different approaches.