Study of adsorption mechanism of chalcone derivatives on mild steel-sulfuric acid interface

Abstract

Chalcone derivatives namely: (E)-3-(4-methoxyphenyl)-1-(p-tolyl)prop-2-en-1-one (MTP), (E)-1,3-di-p-tolylprop-2-en-1-one (DTP), and (E)-3-(4-(diethylamino)phenyl)-1-(p-tolyl)prop-2-en-1-one (DEP) were synthesized and characterized by nuclear magnetic resonance (NMR), Mass spectroscopy (MS) and Infrared spectroscopy (IR). The corrosion mitigation of mild steel (MS) in 0.5 M H2SO4 by these compounds has been investigated by weight loss, electrochemical technique, surface analysis and theoretical studies. The investigations were performed at three optimum concentrations (10−4, 10−5, and 10−6 M) at three temperatures (298, 313 and 328 K) The weight loss Potentiodyanamic polarization (PDP) and Electrochemical impedance spectroscopy (EIS) measurements showed that DEP has the maximum inhibition efficiency (93.3% for highest concentration i.e. 10−4 M) at 298 K among all three inhibitors. The inhibition efficiencies vary directly and inversely with respect to concentration and temperature respectively for all the additives. Potentiodynamic polarization (PDP) measurements revealed that the chalcones are mixed-type corrosion inhibitors and obeyed the Langmuir adsorption isotherms. Electrochemical impedance spectroscopy (EIS) technique further proposes that the inhibitor molecules mitigate corrosion process by adsorbing at the metal/electrolyte interfaces. Further the adsorption of chalcones at the metallic surface was supplemented by SEM and AFM studies where the decreased surface roughness of the inhibited mild steel specimens was observed as compared to the uninhibited specimen. Several thermodynamic parameters (ΔGads0,ΔHads0andΔSads0), DFT and MD theoretical parameters were calculated to explain the adsorption behaviour of these compounds on specimen surface.