Anti-corrosion behaviour of 4(p-tolyldiazenyl)-2-((E)-(p-tolylimino)methyl)phenol on mild steel in 1M H2SO4: Experimental and theoretical studies

The corrosion of mild steel in 1M H(2)SO(4 )solution was significantly inhibited by a new azo Schiff base, 4(p-tolyldiazenyl)-2-((E)-(p-tolylimino)methyl)phenol (ASBm) using both the weight loss and hydrogen evolution methods. The inhibition efficiency increased with increase in ASBm concentration in the temperature range of 30 degrees C to 50 degrees C, but decreased at 60 degrees C. Based on experimental results, chemisorption has been proposed for the inhibition effect of ASBm on mild steel surface at 30 degrees C - 50 degrees C while physisorption is proposed to occur at 60 degrees C. Thermodynamic parameters reveal that the adsorption process was both endothermic and spontaneous. The adsorption of ASBm obeyed Freundlich adsorption isotherm. The protonated species ASBm-H(+ )had proton on N23 atom. Quantum chemical parameters of ASBm and ASBm-H+ were calculated and discussed. Based on Fukui indices, electrophilic centres on ASBm and ASBm-H+ were O16 (0.069) and N9 (0.062), respectively. Conversely, nucleophilic sites on ASBm and ASBm-H+, respectively, are N9 (0.131) and C24 (0.159). Molecular dynamics simulation results reveal that ASBm had a higher binding energy on Fe(110) surface at lower temperatures (30 degrees - 40 degrees C) while the binding energy of ASBm-H+ was higher at higher temperature (50 degrees - 60 degrees C). The contributions by ASBm fragments to the binding energy on Fe(110) surface have been discussed. (C) 2019 The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.