The effect of some prepared compounds, namely thiazole derivatives oil the corrosion of C-steel in 2 M HCl solutions has been studied Using the weight loss and electrochemical polarization methods. The results showed that the inhibition efficiency of the investigated compounds was found to depend on the concentration and the nature of the inhibitor. The presence of the Substituted donating group) (-OCH3) plays an important role in the inhibition percentage ofthese investigated COMPOUnds. The effect of temperature oil the corrosion behavior of C-stccl in 2 M HCl without and with the inhibitors was studied in the temperature range from 30 to 50 degrees C. The activation and thermodynamic parameters E-a* Delta H* and Delta S* were calculated. The inhibitors were adsorbed on the C-steel surface according to Frumkin's adsorption isotherm. The synergistic effect of some cations (Cu2+, Ni2+, CO2, and Ca2+) on the corrosion inhibition of C-steel in 2 M HCl in the presence and absence of the investigated compounds was also studied by the weight loss method.