The isotherm slope. A criterion for studying the adsorption mechanism of benzotriazole on copper in sulphuric acid

D M Bastidas,R R Gómez,E Cano

doi:10.3989/revmetalm.2005.v41.i2.192

Abstract

The adsorption of benzotriazole (BTA) on copper surfaces in 0.001, 0.005 and 0.01 M concentrations of sulphuric acid was investigated using gravimetric measurements. BTA was tested in concentrations from 1x10 -5 to 1x10 -1 M at temperatures from 298 to 328 K. The adsorption mechanism is discussed in terms of applicability of the conventional Frumkin, Bockris-Swinkels and Kastening-Holleck isotherms, among others. The best fit was obtained using the Frumkin isotherm model. The projected molecular area of BTA was calculated to elucidate inhibitor orientation in the adsorption process

Highlights

Copper is widely used in many applications such as heat exchangers, condensers, heating and air conditioning systems, electricity, electronic circuitry and ornamental parts
Benzotriazole (BTA) is an effective corrosion inhibitor for copper in acid solutions^ \ Basically two mechanisms have been proposed in the literature: the adsorption of single BTA molecules on the copper surface and the formation of a protective polymeric film involving the complex ions Cu(I) and [(Cu)^(BTA)1^t^'^°l despite the widespread use of BTA no consensus has been reached on its mechanism
The aim of this paper is to study the inhibition mechanism of BTA on copper electrode surfaces in a sulphuric acid solution, based on analysis of the properties of the thermodynamic isotherms including the interaction term (/) parameter (Temkin, Frumkin, Hill-de Boer and Parsons equations), the configurâtional term (x) parameter (Flory-Huggins, Dhar-Flory-Huggins and BockrisSwinkels equations), and both / and X parameters ( Damaskin-Parsons and Kastening-HoUeck equations)

Summary

Introduction

Copper is widely used in many applications such as heat exchangers, condensers, heating and air conditioning systems, electricity, electronic circuitry and ornamental parts. Benzotriazole (BTA) is an effective corrosion inhibitor for copper in acid solutions^ \ Basically two mechanisms have been proposed in the literature: the adsorption of single BTA molecules on the copper surface and the formation of a protective polymeric film involving the complex ions Cu(I) and [(Cu)^(BTA)1^t^'^°l despite the widespread use of BTA no consensus has been reached on its mechanism. Some authors propose a flat orientation on the surface and bonding through the lone-pair nitrogen orbitals, with lone nitrogen atoms bonded to two copper atoms^ ' ^ K The loss of the imino hydrogen converts each BTA molecule into a (BTA)" ion, with a conjugated K structure delocalised over the three nitrogen atoms^ ^ ^"^K It () Trabajo recibido el día 20 de septiembre de 2004 y aceptdo en su forma final el día 14 de enero de 2005.

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