The effect of Ampicillin (AMP) molecule on the corrosion resistance of stainless steel (SS) is studied using weight loss, open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy in 0.5 mol L-1 HCl solution. The results obtained by weight loss measurements were in good agreement with those obtained by the potentiodynamic polarization and by the electrochemical impedance spectroscopy. These results showed that Ampicillin is a good inhibitor for stainless steel in 0.5 mol L-1 HCl. The inhibition efficiency was found to increase with concentration of the inhibitor. The adsorption of Ampicillin on the stainless steel was found to be physical, exothermic, spontaneous and fitted the Langmuir adsorption model.
