Anticorrosive Effects of Derivatives of 4-{[4-(Dimethylamino) Benzylidene]amino}-1,2,4-Triazole on 316 Stainless Steel in HCl Medium: Experimental and Computational Study

Inhibiting potentials of three Schiff bases derived from 4-(dimethylamino)benzaldehyde, namely 5-(chloromethyl)-4-{[4-(dimethylamino)benzylidene] amine}-4H-1,2,4-triazole-3-thiol (CDTT), 4-{[4-(dimethylamino)benzylidene]amine}-5-phenyl-4H-1,2,4-triazole-3-thiol (DPhTT) and 4-{[4-(dimethylamino)benzylidene]amine}-5-pyridyn-4-yl-4H-1,2,4-triazole-3-thiol (DPyTT) on the corrosion of 316 stainless steel (316 SS) in 2M HCl were evaluated using weight-loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods at different inhibitor concentrations (5 to 500 ppm) and different temperatures (30 to 60 degrees C). DPhTT displayed a maximum inhibiting performance of 94.21% at 500 ppm at 30 degrees C. The inhibitors CDTT and DPyTT showed inhibition efficiencies of 85.38% and 85.23% under similar conditions. All three inhibitors inhibited both cathodic and anodic corrosion processes. The enthalpies of activation for DPhTT, CDTT and DPyTT were 22.85, 36.23 and 50.86 kJ/mol, respectively, for 500 ppm solutions suggesting endothermic nature of the process. Adsorption of the inhibitors on the surface of the alloy was compatible with the Langmuir isotherm. Thermodynamic parameters of adsorption indicated that adsorption is primarily performed through chemisorption. The findings of EIS confirmed the formation of a chemisorbed film on the surface of the alloy. The scanning electron microscopy (SEM) and energy-dispersive x-ray studies (EDS) provided more evidence of increased corrosion resistance of 316 SS in the presence of inhibitors. Density functional theory (DFT) calculations have confirmed the experimental findings.