Halogen-substituted thiazole derivatives as corrosion inhibitors for mild steel in 0.5 M sulfuric acid at high temperature

The inhibitory effects of three halogen-substituted thiazole derivatives named 2-amino-4-(4-fluorophenyl)-thiazole (FPT), 2-amino-4-(4-chlorophenyl)-thiazole (CPT) and 2-amino-(4-bromophenyl)-thiazole (BPT) on mild steel corrosion were investigated in 0.5 M H ₂ SO ₄ from 30 °C to 60 °C. Electrochemical measurements demonstrated that these thiazoles can effectively inhibit the corrosion of mild steel in 0.5 M H ₂ SO ₄ solution at 30 °C. With the increase of temperature, the inhibition efficiency (η) of FPT at 60 °C reduced to 22.62% while those of CPT and BPT under the same temperature were nearly unchanged, which were as high as 95.16% and 95.45%, respectively. The adsorptions of three thiazoles on the surface of mild steel were all found to adhere to Langmuir adsorption isotherm at 30 °C while only CPT and BPT obeyed at 60 °C. Quantum calculations results indicated that CPT and BPT had the better adsorption ability on mild steel than FPT. Molecular dynamic stimulations were taken out to investigate the adsorption configurations of three thiazoles on the surface of Fe (0 0 1) at 30 °C and 60 °C, and the results implied that the binding energy of protonated BPT and CPT were nearly unchanged at studied temperatures while that of protonated FPT apparently became lower at 60 °C.