Substituted benzotriazoles as inhibitors of copper corrosion in borate buffer solutions

Resumo

The adsorption of substituted 1,2,3-benzotriazoles (R-BTAs) onto copper is measured via ellipsometry in a pure borate buffer (pH 7.4) and satisfactorily described by Temkin’s isotherm. The adsorption free energy (−ΔG_a⁰) values of these azoles are determined. The (−ΔG_a⁰) values are found to rise as their hydrophobicity, characterized by the logarithm of the partition coefficient of a substituted BTA in a model octanol–water system (logP), grows. The minimum concentration sufficient for the spontaneous passivation of copper (C_min) and a shift in the potential of local copper depassivation with chlorides (E_pt) after an azole is added to the solution (i.e., ΔE = E_ptⁱⁿ − E_pt^backgr characterizing the ability of its adsorption to stabilize passivation) are determined in the same solution containing a corrosion additive (0.01М NaCl) for each azole under study. Both criteria of the passivating properties of azoles (logC_min and ΔE) are shown to correlate linearly with logP, testifying to the role played by surface activity of this family of organic inhibitors in protecting copper in an aqueous solution.