Experimental and theoretical approach for a better understanding of the mechanisms of adsorption and inhibition of corrosion for carbon steel by thiazolidine derivatives in 1 M HCl medium.

Many sectors have employed various strategies to prolong the life of steel because of its strength and high manufacturing and installation costs. The use of organic inhibitors has been widespread in recent years. The purpose of this investigation is to evaluate the activity of recently synthesized derivatives, namely ( Z )-5-benzylidenethiazolidine-2,4-dione (FT-2a), ( Z )-5-(2,4-dichlorobenzylidene)thiazolidine-2,4-dione (FT-2c), and ( Z )-3-allyl-5-(2,4-dichlorobenzylidene)thiazolidine-2,4-dione (FT-3c), in inhibiting corrosion through electrochemical assays on carbon steel (CS) in 1 M HCl at 303 K. The chosen products (FT-2a, FT-2c, and FT-3c) were selected as corrosion inhibitors due to their eco-friendly composition and biodegradability, aligning with the increasing demand for sustainable products. The findings revealed that the inhibitory activities of FT-2a, FT-2c, and FT-3c improved with increasing concentration, reaching maximum values of 94.10%, 95.30%, and 96.50% for FT-2a, FT-2c, and FT-3c, respectively. In contrast, the corrosion mitigation effectiveness decreased by around 22.69% (for FT-2a), 18.87% (for FT-2c), and 17.81% (for FT-3c) with the rise in temperature from 303 to 333 K. An overview of potentiodynamic polarization (PDP) plots revealed that the three products function as mixed-type inhibitors and adsorb according to the Langmuir isotherm in the corrosive 1 M HCl solution. Surface analysis [scanning electron microscopy (SEM-EDX), contact angle (CA), and X-ray diffraction (XRD)] of the CS specimens demonstrated that the chosen inhibitors were absorbed and formed protective layers that mitigated the impact of corrosion. Strong interactions between FT-2a, FT-2c, and FT-3c molecules and Fe ions at particular atomic sites were identified by analysis of UV-visible spectra. Using techniques such as Fukui functions, molecular dynamics simulations (MDS), and DFT calculations, the impact of the molecular structure of FT-2a, FT-2c, and FT-3c on their capacity to suppress corrosion was investigated. In addition, the protonation of thiazolidine derivatives in acidic media was studied. The results of these various methods were very coherent.