Studies on the effect of a newly synthesized Schiff base compound from phenazone and vanillin on the corrosion of steel in 2 M HCl

The inhibiting action of a Schiff base 4-[(4-hydroxy-3-hydroxymethyl-benzylidene)-amino]1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (phv), derived from 4-amino-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (phz) and 4-hydroxy-3-methoxy-benzaldehyde (vn), towards the corrosion behavior of steel in 2 M HCl solution has been studied using weight loss, polarization and electrochemical impedance spectroscopy (EIS) techniques. Although vn and phz were found to retard the corrosion rate of steel, the compound synthesized from vn and phz was seen to retard the corrosion rate even more. At constant temperature, the corrosion rate decreases with increasing inhibitor concentration. However, at any inhibitor concentration the increase in temperature leads to an increase in the corrosion rate of steel. The activations energies, Delta E-a, as well as other thermodynamic parameters (Delta G(ads)(o), Delta H-ads(o)) for the inhibitor process were calculated. The inhibitor efficiencies calculated from all the applied methods were in agreement and were found to be in the order: phv > phz > vn. (C) 2005 Elsevier Ltd. All rights reserved.