ANODIC POLARIZATION BEHAVIOR OF COPPER IN AQUEOUS BROMIDE AND BROMIDE BENZOTRIAZOLE SOLUTIONS

Theoretical potential-pH equilibria and anodic polarization studies were used to show that formation of the aqueous CuBr2- complex in 1M NaBr at similar to 24 degrees C promotes active behavior of copper at pH values greater than or equal to 3 < 7 in a manner similar to that observed in chloride solutions. A region of apparent Tafel behavior is observed with a position and slope (dE/d log i) of 60 mV that is consistent with mass transport control of the CuBr2- species. Careful analysis of this region provides a method for checking the value of the chemical-free energy of the cuprous complex. Polarization studies in benzotriazole containing 1M NaBr show that benzotriazole interacts with the active oxide-free copper surface to inhibit anodic dissolution of copper. The interaction is potential-dependent, similar to the behavior in chloride solutions, and inhibition is less effective at the lower pH values. Furthermore, a potential occurs above which the spontaneous repair of a damaged inhibiting film is unlikely. The inhibition process is discussed and the observations are shown to be reasonably consistent with a mechanism whose first step is the adsorption of the neutral benzotriazole molecule. Some possible similarities and differences between the active behavior of copper in iodide and bromide solutions are discussed on the basis of differences in their potential-pH equilibria.