CORROSION INHIBITORY EFFECT OF FEW PIPERIDIN-4-ONE OXIMES ON MILD STEEL IN HYDROCHLORIC ACID MEDIUM

Abstract

Three piperidin-4-one oxime derivatives viz. 3,5-dimethyl-2,6-diphenyl-piperidin-4-one oxime (DDPO), 3-ethyl-2,6-diphenyl-piperidin-4-one oxime (EDPO), and 1-methyl-3-isopropyl-2, 6-diphenyl-piperidin-4-one oxime (MIDPO) were synthesized. Corrosion inhibiting ability of these compounds in 1 M HCl was studied using weight loss study, potentiodynamic polarization measurements, electrochemical impedance spectroscopy, XRD and SEM with EDS measurements. Weight loss studies revealed that all the three oximes are good corrosion inhibitors. The order of inhibiting ability of these compounds is as follows: DDPO > EDPO > MINDO. Results of the polarization measurement showed that these inhibitors do not alter the mechanism of either hydrogen evolution or mild steel dissolution reaction, proving the mixed mode of inhibition. At constant acid concentration, increase of inhibitor concentration increased the charge transfer resistance (R ct ), complimented with decrease of double layer capacitance (C dl ), thereby indicating the increase of percentage inhibition efficiency. XRD and SEM with EDS analysis provided strong proof for the existence of inhibitor film over the mild steel surface.