Abstract: The adsorption and inhibition effect of Tween40 on cold rolled steel (CRS) in 1.0~8.0 mol/L hydrochloric acid has been studied by weight loss method.The results showed that Tween40 was a good inhibitor in 1.0 mol/L HCl,and the maximum inhibition efficiency was 92.47% even when the inhibitor concentration was low.Inhibition efficiency decreased with the increase of hydrochloric acid concentration and temperature.The experimental data have been treated with adsorption theory,the thermodynamic parameters have been obtained.The thermodynamic results showed that the adsorption of Tween40 on the cold rolled steel surface obeyed the Langmuir adsorption isotherm equation.Furthermore,the adsorption process was a spontaneous and exothermic process accompanied by a decreasing entropy.