Transients of Corrosion Morphology and Weight Loss of Cu in Concentrated LiBr Aqueous Solution

This research aimed to investigate transients of corrosion morphology and weight loss of Cu in concentrated LiBr aqueous solution for understanding corrosion process of copper parts in an absorption heat pump. Cu plate specimens were immersed in an aqueous solution containing 65 mass% LiBr and 0.2 mass% LiOH at 353 K for various times, and then subjected to weight measurement tests and surface analysises. The specimen immersed in the solution suffered pit-like corrosion. The number of the pit increased linearly with an increase in an immersion time until 691.2 ks, and thereafter almost no pit was initiated. Each pit was semi-spheroid, and grew at a constant rate in each direction of horizontal and vertical. A corrosion weight loss showed an accelerated increase as an immersion time elapsed. The transients of the weight loss until 1728 ks was successfully simulated by assuming the corrosion process of the initiation and the growth of the pits. The simulation also revealed that a corrosion area was in good agreement with the whole specimen surface in around 1728 ks, and then that aspect of the corrosion shifted from pit-like corrosion to general corrosion. The empirical corrosion rate after 1728 ks obtained by the weight measurement test was also in good agreement with the vertical growth rate of the pit.