Evolution with Exposure Time of Copper Corrosion in a Concentrated Lithium Bromide Solution. Characterization of Corrosion Products by Energy-Dispersive X-Ray Analysis and X-Ray Diffraction

The evolution with the exposure time of copper corrosion in a 400-g/L lithium bromide (LiBr) solution was investigated using electrochemical measurements. The study was carried out under a hydrodynamic regime in the absence of oxygen. As time passes, the cathodic diffusion-limited current density (ųfl and the anodic Tafel slope (β_a) increase, and from a given time they begin to decrease until reaching a nearly constant value. β_a changes are due to a balance between activation and diffusion control and not to a change in the copper dissolution reaction. The steady state is the result of a balance between the separation from the surface of the corrosion products precipitated—due to the fluid flow—and the deposition of the new corrosion products formed; this leads to a limiting film thickness and a nearly constant diffusion rate. The corrosion products were characterized by energy-dispersive x-ray (EDX) analysis and by x-ray powder diffraction. Data show the corrosion products could be a mixture of hydroxides, oxides, and copper bromide where copper is mainly present in the Cu(II) state; so, it would imply an evolution from Cu(I) to Cu(II).