ISOXAZOLINE DERIVATIVES AS INHIBITORS FOR MILD STEEL CORROSION IN 1M H2SO4: COMPUTATIONAL AND EXPERIMENTAL INVESTIGATIONS

Abstract

The isoxazoline derivatives namely 3-phenylamino-5-(3′-methoxy-4′-hydroxyphenyl) isoxazoline (PAMHI), 3-phenylamino-5-(4′-methoxyphenyl)isoxazoline (PAMI) and 3-phenylamino-5-(4′-hydroxyphenyl)isoxazoline (PAHI) were synthesized and tested for their inhibition capacity against the mild steel (MS) corrosion in 1 M H2SO4. Their inhibition performance toward MS has been studied through well-known methods namely weight loss (WL), electrochemical and surface analysis. The inhibition efficiency of PAMHI was 95.90% at 10mM concentration. The adsorption studies indicated that the isoxazoline derivatives obeyed Langmuir adsorption isotherm on the mild steel surface, and Gibbs free energy values were in the range of -32.05, -28.52 and -33.44 kJ mol-1. These results suggested that the inhibitor molecules interacted with the mild steel surface through mixture adsorption. Also, mixed type behavior was observed for the studied inhibitors from polarization studies. The presence of a protective layer of organic matter was validated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Density-functional theory (DFT) method and molecular dynamics (MD) simulation have been studied and the results shown that the inhibitory efficiencies of the three molecules tested are almost the same.