Experimental and theoretical assessment of new and eco-friendly thioglycoluril derivative as an effective corrosion inhibitor of St2 steel in the aggressive hydrochloric acid with sulfate ions

The new and eco-friendly corrosion inhibitor based on thioglycoluril derivative (2-thioxo-5,5-di-p-toly limidazolidin-4-one (TODTI)) for St2 steel in 1 M HCl + 1 M Na2SO4 solution was first introduced and its inhibition properties were first fully characterised by gravimetric, thermodynamic, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), electrochemical noise (EN), electrochemical frequency modulation (EFM), density functional theory (DFT), molecular dynamics (MD) simulations, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) methods. The effect of thioglycoluril rings on the St2 steel inhibition and salt-corrosion on the St2 steel surface was first studied. The experimental results indicated that TODTI had excellent inhibition abilities (96.72% at 200 mg/L/0.675 mM) at medium temperatures (303-333 K); the St2 steel was maximally inhibited and salt-corrosion was importantly reduced with the adsorption of thioglycoluril rings on the metal surface in the aggressive hydrochloric acid with sulfate ions. The electrochemical investigations revealed that TODTI is a mixed-type corrosion inhibitor, and its adsorption nature was confirmed according to the Langmuir isotherm. The quantum chemical calculations confirmed a good correlation with the experimental results and indicated that the inhibitory nature of TODTI is linked to its quantum chemical characteristics. (C) 2021 Elsevier B.V. All rights reserved.