Inhibition of Corrosion of Mild Steel in Hydrochloric Acid Solution by two Schiff Bases Derived from Benheric and Linoleic Acids

Abstract

Communication in Physical Sciences 2019, 4(2): 58-66

Author: S. A. Odoemelam, U. I. Ekanem & F. K. Ekuma 

The inhibition efficiencies of the two Schiff bases 2[2-diethylamino) ethyl methyl amino)-4- methy1-5-3 (3-methyl sulfanyl propy1 amino) methyldiene cyclohexdien-1-one (DEMS) and [1- (azepan-1-yl)2-2-[4-(2-tert-butyl sulfanyl ethyl piperazin-1-yl] ethanone (ATSP), synthesized from linoleic and benheric acids on the corrosion of mild steel in 1 M HCl solutions were investigated using gravimetric and potentiodynamic polarization techniques.. The results obtained from both methods indicated that inhibition efficiencies increased with increase in concentration of the Schiff bases and decreased as the temperature increased. Potentiometric polarization data indicated decrease in polarization resistance (and a corresponding decrease in corrosion current) with concentration, which indicated a progressive retardation of corrosion strength with increasing concentration.
Displacement potential from the reference blank and equality of extension of cathodic and anodic polarization curves confirmed that DEMS and ATSP are mixed type inhibitor. Mechanism of adsorption of the inhibitors was confirmed to be physiosorption based on calculated values of activation energy and the changes in free energy of adsorption. The adsorption of the inhibitors is spontaneous, exothermic and followed the Langmuir adsorption model.