Effect of three component (aniline–formaldehyde and piperazine) polymer on mild steel corrosion in hydrochloric acid medium

Polymeric Schiff base containing aniline, formaldehyde and piperazine (AFPP) was synthesized and investigated as corrosion inhibitor for mild steel in 1 M HCl by weight loss measurements, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Experimental results showed that AFPP is an effective inhibitor for mild steel in 1 M HCl and exhibited 98% inhibition efficiency. Potentiodynamic polarization studies showed that AFPP is a mixed-type inhibitor predominantly cathodic type. The adsorption of inhibitor on the mild steel surface followed Langmuir adsorption isotherm. Activation energy (Ea), standard energy of adsorption (ΔG°ads), enthalpy of activation (ΔH∗), and entropy of activation (ΔS∗) of corrosion process were calculated and discussed.