Kinetics of corrosion inhibition of benzotriazole to copper in 3.5% NaCl

The kinetics of interaction of benzotriazole (BTAH) with the surface of copper were studied using an electrochemical quartz crystal microbalance (EQMB) and electrochemical impedance spectroscopy (EIS). Upon injecting BTAH into the electrolyte, three regions appear in the time response of the microbalance. Region I (at short time scale of few minutes) exhibits rapid linear growth of mass with time. This is attributed to the formation of a Cu(I)BTA film that is several hundred layers thick. Region II reveals adsorption of BTAH at a slower rate, on the inner Cu(I)BTA complex. Region III is a plateau indicating that the BTAH film attains an equilibrium thickness, which increases with the concentration of BTAH. The polarization resistance of the interface changes with time in a similar fashion while the double layer capacitance decreases. The results suggest that the thickness of the physically adsorbed film of BTAH increases with time and BTAH concentration while the thickness of the inner Cu(I)BTA remains constant. Two semicircles were obtained in the impedance spectra corresponding to the complex Cu(I)BTA and the physically adsorbed BTAH.