Synthesis, characterization and evaluation of a novel thiazolidinone derivative as a corrosion inhibitor for C38 steel in 1 M HCl medium: experimental and DFT analysis

To explore the corrosion behavior of carbon steel (C38) in acidic environments, both experimental and computational methods were employed to evaluate the newly synthesized thiazolidinone product, 2-((3,5,5-trimethylcyclohex-2-en-1-ylidene)hydrazono)thiazolidinone (Isophoron-Thiazolidinone IT), as a corrosion inhibitor for C38 steel in 1 M HCl solution. Characterization techniques, including IR, NMR, spectroscopy, and MS, confirmed the successful synthesis of IT with a yield of 81 %. Experimental tests, including weight loss measurements (WL), EIS, and PDP, demonstrated that IT acts as a mixed-type inhibitor, achieving a peak inhibition efficiency of 96.56 % under optimal conditions (5 × 10⁻³ mol L⁻¹ at 298 K). These results were confirmed through surface analysis using Scanning Electron Microscopy (SEM), which showed that IT molecule adsorb onto the C38 surface, creating a protective layer that prevents corrosion and reduces oxidation. The adsorption of IT on the C38 surface followed the Langmuir adsorption isotherm, indicating a combination of physical and chemical adsorption processes, leading to the formation of a dense, uniform protective film. Computational studies using DFT supported these experimental observations, identifying reactive centers in IT and confirming its efficacy as a corrosion inhibitor.