Effect of Aqueous Lithium Bromide Solutions on the Corrosion Resistance and Galvanic Behavior of Copper-Nickel Alloys

The analysis of the corrosion of Cu-xNi alloys (x = 10 wt% to 30 wt%) and Cu and Ni metals in commercial lithium bromide (LiBr) heavy brine solutions, with and without additives, was performed by polarization curves. Corrosion rates were determined by the Tafel slope method, and inhibitor effects were analyzed in the commercial solution. Critical potentials were calculated at 50 μA and it was observed that the nickel content shifted critical potentials to more positive values. Breakdown potentials were calculated in commercial LiBr solution. Galvanic current and mixed potentials were determined using polarization curves according to the mixed potential theory. The results demonstrate that only under particular conditions of pH and concentration of LiBr solution, alloying with nickel improved corrosion resistance of an alloy. In fact, it was observed that the inhibition effect of commercial LiBr (additive with chromate) was always higher for the copper electrode and lower for the nickel one. Commercial solution shifted open-current potentials and critical potentials to more positive values. The galvanic behavior of the studied alloys did not follow a common and generalized character in function of the metallic components of the materials and LiBr concentration. It is only possible to generalize that the most negative mixed potentials and the lowest galvanic current were measured in commercial LiBr solution.