Influence of copper cation on inhibition of corrosion for steel in presence of benzotriazole sulfuric acid

The concentration influence of benzotriazole on the electrochemical and corrosion behaviour of steel with and without a copper cation was studied potentiokinetically. It was found that benzotriazole increases the polarization resistance to a great extent. It was found that the Cu cation, at a concentration of 10(-3) M, strongly inhibits the corrosion rate. The corrosion of the steel in 0.1 M H2SO4 is appreciably reduced by benzotriazole in combination with the metallic copper cation, as a result of co-adsorption. At a higher concentration of copper cation (10(-2) M) in association with benzotriazole, the dissolution of steel is increased owing to the cathodic reduction of the cation to metal, and the potential is shifted toward the electropositive direction. In the presence of benzotriazole and lower metallic copper cation concentrations (10(-4) M), the potentials shift in the electronegative direction, indicating suppression of the cathodic reaction by co-joint adsorption of the inhibitor and metallic cation. The kinetic and thermodynamic parameters were calculated at different temperatures. The negative temperature coefficient for corrosion inhibition is assuming that the corrosion reaction is no longer the simple metal/acid reaction, owing to adsorption retardation. (C) 1998 Elsevier Science S.A. All rights reserved.