Condensed Fukui function and experimental evaluation of the corrosion inhibition properties of some antipyrinyl‐imidazotriazole and their derivatives for copper in an acidic environment

Abstract

Abstract The effectiveness of synthesized antipyrinyl‐imidazotriazole and its derivatives as inhibitors for the corrosion of copper alloy in 0.5 M H 2 SO 4 solution was tested using weight loss, electrochemical impedance spectroscopy (EIS) and potentiodyanmic polarization techniques. The generated results confirmed that the tested compounds have strong inhibition efficiencies for the protection of the corrosion of copper alloy in 0.5 M H 2 SO 4 . Maximum inhibition efficiencies (IEs) evaluated from electrochemical measurements at inhibitor's concentrations of 0.040 g/L were 85% (5‐(4‐Antipyrinyl)‐3 H ‐imidazo[1,2‐ b ][1,2,4]triazole), 60% (6‐Antipyrinyl‐imidazo[2,1‐ b ]thiazole) and 72% (2‐Antipyrinyl‐7‐ethoxy‐imidazo[2,1‐ b ]benzothiazole). It was observed that the inhibition efficiency was strongly influenced by the flow rate of the solution and was reduced to 79 (5‐(4‐Antipyrinyl)‐3 H ‐imidazo[1,2‐ b ][1,2,4]triazole), 60% (6‐Antipyrinyl‐imidazo[2,1‐ b ]thiazole), and 44% (2‐Antipyrinyl‐7‐ethoxy‐imidazo[2,1‐ b ]benzothiazole) at an agitation speed of 400 rpm. EI from weight loss was comparable with those from PDP of mixed‐type inhibition style and EIS of diffusion model. The low inhibition efficiency for 6‐Antipyrinyl‐imidazo[2,1‐ b ]thiazole was significantly enhanced from 60% to 90% through a synergistic effect of 0.0001 M KI. The Temkin and Frumkin isotherms indicate the physical adsorption of inhibitors on copper surface. Condensed Fukui function calculations reveal a common center for electrophilic attacks in the three molecules: the nitrogen in the bridged pyrrole rings (labeled as N11).