4,5-Diphenyl-1H-Imidazole-2-Thiol ( DIT ) has been evaluated as a corrosion inhibitor for C 38 steel in 1 M HCl by gravimetric method. The effect of DIT on the corrosion rate was determined at various co ncentrations. The effect of the temperature on the corrosion behavior with addi tion of the optimal concentration of DIT was studied in the temperature range 298 – 328 K. The DIT acts as an effective corrosion inhibitor for C38 i n hydrochloric acid medium. The inhibition process is attributed to the formation of an adsorbed film of DIT on the metal surface which protects the metal against corrosion. The protectio n efficiency increased with increase in temperatur e. Adsorption of DIT on the C38 steel surface is found to obey the Lang muir adsorption isotherm. Some thermodynamic functi ons of dissolution processes were also determined.