The effect of addition of 2, 6-diphenylpiperidin-4-one semicarbazone on the corrosion of steel in 1M HCL acid has been studied by weight loss measurements and potentiodynamic polarization measurements. The inhibition efficiency was found to increase with inhibitors content to attain 61.00% and 79.66%2, 6-diphenylpiperidin-4-one semicarbazone respectively. Data obtained from weight loss measurements and potentiodynamic polarization measurements studies were analyzed to determinate the model inhibition process. Inhibition efficiency E (%) obtained from the various methods is in good agreement.