Thermodynamic, electrochemical and quantum chemical evaluation of some triazole Schiff bases as mild steel corrosion inhibitors in acid media
摘要:
Three newly synthesised triazole Schiff bases (3-bromo-4-fluoro-benzylidene)-[1,2,4]triazol-4-yl-amine (BEST), (4-trifluoromethyl-benzylidene)-[1,2,4]triazol-4-yl-amine (TMBT) and (2-fluoro-4-nitro-benzylidene)[1,2,4]triazol-4-yl-amine (FNBT) were investigated as corrosion inhibitors on mild steel in 0.5 M hydrochloric add by chemical (weight loss) and electrochemical (potentiodynamic polarisation and electrochemical impedance) techniques. The inhibition efficiency increases with an increase in inhibitor concentration and decreases with an increase in temperature of the medium. Various activation and adsorption thermodynamic parameters were evaluated. Adsorption of all the three inhibitors follows the Langmuir isotherm. Electrochemical impedance studies show that charge transfer resistance increases with concentration of inhibitors. Polarisation studies prove that inhibitors are of the mixed type. Surface morphology was examined using SEM and FTIR studies. Quantum chemical calculations give evidence to experimental results. Higher value of E-HOMO, lower value of E-LUMO,E- smaller orbital gap (Delta E) and higher dipole moment makes BFBT superior over TMBT and FNBT thus shows the maximum inhibition efficiency. All the studied methods are showing good correlation with each other. (C) 2015 Elsevier B.V. All rights reserved.
Three newly synthesised triazole Schiff bases (3-bromo-4-fluoro-benzylidene)-[1,2,4]triazol-4-yl-amine (BEST), (4-trifluoromethyl-benzylidene)-[1,2,4]triazol-4-yl-amine (TMBT) and (2-fluoro-4-nitro-benzylidene)[1,2,4]triazol-4-yl-amine (FNBT) were investigated as corrosion inhibitors on mild steel in 0.5 M hydrochloric add by chemical (weight loss) and electrochemical (potentiodynamic polarisation and electrochemical impedance) techniques. The inhibition efficiency increases with an increase in inhibitor concentration and decreases with an increase in temperature of the medium. Various activation and adsorption thermodynamic parameters were evaluated. Adsorption of all the three inhibitors follows the Langmuir isotherm. Electrochemical impedance studies show that charge transfer resistance increases with concentration of inhibitors. Polarisation studies prove that inhibitors are of the mixed type. Surface morphology was examined using SEM and FTIR studies. Quantum chemical calculations give evidence to experimental results. Higher value of E-HOMO, lower value of E-LUMO,E- smaller orbital gap (Delta E) and higher dipole moment makes BFBT superior over TMBT and FNBT thus shows the maximum inhibition efficiency. All the studied methods are showing good correlation with each other. (C) 2015 Elsevier B.V. All rights reserved.