Synthesis of 4-methylthiazol-2(3H)-thione derivatives and their application as corrosion inhibitors: weight loss, electrochemical, XPS and theoretical study

The corrosion inhibition of C38 steel in 1M HCl by isomeric derivatives of 4-methylthiazol-2(3H)-thione (TO1, TO4 and TO6) has been investigated using weight loss and electrochemical measurements supplementing with surface characterization study using X-ray photoelectron spectroscopy (XPS). Experimental observations were found to be in agreement with density functional theory (DFT) calculations. The inhibition efficiency increases with increase in the three compounds concentration and showed maximum inhibition efficiency of 98.33%, 96.91% and 94.44% for TO1, TO4 and TO6 at 2.10-4M in HCl 1M, respectively, at concentration of 2×10-4 M at 30°C. Polarization curves reveal that the three inhibitors act as mixed type inhibitor with tendency to anodic branch. Impedance parameters (charge transfer resistance, Rt, and double-layer capacitance, Cdl) indicate that the investigated compounds form stable protective films on the steel surface. Adsorption of TO1, TO4 and TO6 on the C38 steel surface is found to obey the Langmuir adsorption isotherm. The X-ray photoelectron spectroscopy (XPS) of the carbon steel treated with the three compounds indicated that these later are chemically adsorbed on the steel surface. Good correlations were obtained between the anti-corrosion performance of these donor-acceptor compounds and their molecular properties