Effects of Hydrodynamic Conditions and LiBr Concentration on the Corrosion of Copper in LiBr Absorption Machines

Abstract

Refrigeration absorption machines are again considered as suitable refrigeration systems and they are replacing compression machines due to the ban of chlorofluorocarbons (CFCs) and the strict regulations of hydrochlorofluorocarbons. Lithium Bromide (LiBr) is one of the most widely used absorbents in refrigeration technology. However, the operating conditions of absorption machines (high concentration and high temperature) can cause serious corrosion problems in the structural materials. Corrosion problems can be enhanced by the hydrodynamic conditions of the system. The present work studies of the influence of hydrodynamic conditions on copper corrosion under different LiBr conditions. Polarisation potentiodynamic curves obtained following ASTM G-5 were used to study the influence of the LiBr concentration and hydrodynamic conditions. Parameters such as corrosion current density and corrosion potential were obtained from the potentiodynamic curves. A rotating disk electrode (RDE) was used to determine the hydrodynamic conditions. Three LiBr solutions of different concentration (400 g/l, 700 g/l, and 850 g/l) at 25 degrees C and different rotation rates (0 r.p.m. - 3000 r.p.m.) were used during the tests. Results show that an increase of the bromide concentration and rotation rate favours copper corrosion and enhances anodic dissolution. The effects of the hydrodynamic conditions are smaller at higher LiBr concentrations.