ELECTROCHEMICAL AND THEORETICAL STUDIES INFLUENCING THE EFFECT OF HYDROXYL POSITION OF TETRAPHENOLIC SCHIFF BASES TOWARDS CORROSION INHIBITION OF MILD STEEL IN 1M HCl

Abstract

The effect of three tetrahydroxylated Schiff bases as N,N-bis(2,3-dihydroxybenzylidene)-4,4’-diphenylmethane, N,N-bis(2,4-dihydroxybenzyl- idene)-4,4’-diphenylmethane and N,N-bis(2,4-dihydroxybenzylidene)-4,4’-diphenylmethane were studied as inhibitors for mild steel in 1M HCl medium. The experiments were performed using potentiodynamic polarization. This inhibition proved an efficient increase according the position of second hydroxyl of salicylaldehyde suggesting that this inhibition is dependent on concentration and the compound nature. Among these position-isomers, the best inhibition efficiency was obtained with p-hydroxylated (94%) at 1mM. Tafel plots of these inhibitors are the mixedtype, their adsorption is spontaneous obeying to Langmuir’s isotherm. AFM/SEM-EDS characterized metal surface. DFT-calculations and molecular dynamics simulations are correlated to inhibition efficiency obtained.