Inhibitive and adsorption behavior of new thiazoldinone derivative as a corrosion inhibitor at mild steel/electrolyte interface: Experimental and theoretical studies

Abstract

The target pyrrolyl-thiazoldin-4-one inhibitor (PEHT) was synthesized by the cyclization of 2-acetylpyrrole thiosemicarbazone with ethyl bromoacetate, and its chemical structure was determined by different spectroscopic techniques, such as FT-IR, 1H NMR, and 13C NMR. The PEHT performance, as a mild steel (MS) corrosion inhibitor, in an acidic solution was evaluated by mass loss (ML), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) measurements. The PEHT concentration effect, studied by mass loss, reached maximum protection efficiency at 8 × 10–4 M, 92.6% at 303 K. The PEHT was adsorbed on MS surface chemically and followed Langmuir isotherm, ΔG°ads = −37.30 kJ mol−1 at 303 K, forming a protective film as deduced from EIS data. The PDP measurements revealed that PEHT acted as a mixed-type inhibitor. Further, the MS surface morphology was studied by FT-IR, UV/Vis, SEM and AFM which designated and supported the formation of a protective layer of the PEHT on the surface. Finally, the DFT quantum chemical calculations of PEHT in acidic medium were carried out to investigate the active sites for binding with metal surface.