Synthesis, Characterization and Electrochemical Studies on the Corrosion Inhibition Properties of Schiff Bases for Mild Steel in 1 M HCl Solution

Schiff bases (SBL1 and SBL2), non-toxic compounds were synthesized, characterized and  investigated as alternative anticorrosive additives for inhibition of mild steel corrosion in I M HCl acid medium. Corrosion of the steel was monitored by Potentiodynamic Polarization (PDP), Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS) and Weight Loss (WL) techniques. The novel Schiff base ligands obtained were characterized by Ultraviolet-visible and Fourier-Transform Infrared Spectroscopy. The elemental analysis data for the Schiff base ligands were used to confirm the formula of SBL1 as C17H20N2O2 and SBL2 as C24H21N5O2. Fourier-Transform Infrared spectroscopy suggest that the formation of a complex film on the mild steel surface was due to the adsorption of SBL1 and SBL2. The adsorption process was spontaneous and consistent with the mechanism of physical adsorption as best approximated by the Langmuir adsorption isotherm. Maximum inhibition efficiency was obtained at maximum concentration of 100 ppm for both SBL1 and SBL2 with SBL2 possessing the higher inhibition efficiency (86.21%) more than SBL1 (76.92%). Effectiveness of SBL1 and SBL2 reduced with increase in time and progressed with increase in concentration of SBL1 and SBL2. PDP measurements showed that SBL1 and SBL2 acted as a mixed type inhibitor. EIS measurement reveals that the corrosion process was controlled by charge transfer process. Values of the inhibition efficacy obtained from the different techniques were comparable. SEM micrographs of mild steel surface indicated good surface protection of SBL1 and SBL2.