New Cyanoacetamide Derivatives as Corrosion Inhibitors for Carbon Steel in Acidic Media

Abstract

The corrosion behavior of carbon steel  in 1 M HCl solution in the absence and presence of 4-(2-Cyano-7- hydroxy-4-methylene-hepta-2,5-dienoylamino)-benzoic acid (a), 4-[2-Cyano-3-(4-methoxy -phenyl)-acryloylamino]-benzoicacid.(b), 4-(2-Cyano-3-phenyl acryloylamino)-benzoic acid (c) ,4-[3-(4-Chloro-phenyl)-2-cyano-acryloylamino]-benzoic acid(d), was investigated using weight loss , potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The inhibitive action of the investigated compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structures. The adsorption of these derivatives on carbon steel surface is consistent with Freundlich adsorption isotherm. The effect of temperature on the rate of corrosion in the absence and presence of these compounds were also studied. Physical adsorption mechanism is proposed from the calculated thermodynamic parameters for all investigated compounds.