Synthesis, Corrosion Inhibition and Theoretical Studies of (E)-2-((2,5-Dichlorophenyl)diazenyl)naphthalen-1-ol as Corrosion Inhibitor of Mild Steel in 0.5 M Hydrochloric Acid

Abstract

The inhibitory capacity of (E)-2-((2,5-dichlorophenyl)diazenyl)naphthalen-1-ol (DPD) against mild steel corrosion in 0.5 M HCl has been studied at different temperature (25 – 65 ºC) by gravimetric and electrochemical methods. Quantum chemical study using DFT was employed to explain the experimental results. The corrosion activation energy, E_a, Free energy, ∆G^o_ads, enthalpy, ∆H^o_ads and entropy, ∆S^o_ads, of adsorption were calculated. The inhibition efficiency increases with increase in concentration and decreases with increasing temperature. The adsorption on the mild steel surface was found to follow Langmuir adsorption isotherm while the potentiodynamic polarization revealed DPD as the cathodic type inhibitor. The adsorption occurred via exothermic process and followed physisorption mechanism. The study therefore presented DPD as potential inhibitor of mild steel corrosion in acidic environment.

Keywords: Weight loss, Polarization, Kinetic parameters, Naphthol azo-dye, Inhibition efficiency