Study of copper alloy corrotion in flowing water environments at temperature between 20 and 45ºC

Abstract

Transfer of copper metal by boiler feed water from the condenser tubes to other critical equipment parts of the industrial plant, like steam turbine blades, boiler tubes, can cause serious problems, such as reduction of electricity generation in power plants, boiler failure, and increase production costs, which may ultimately lead to loss of economic viability. Among the factors which affect the corrosion rate of copper alloys in flowing water environments, the relationship between the velocity of feed water and the corrosion rate of copper alloy has not been studied in detail. Therefore, this study investigates the effect of the flow rate of water on the corrosion of copper alloy at different combinations of temperature (between 20 and 45 ºC) and dissolved oxygen concentration (between 6.1 and 9.2 mg/l). All other operating condition variables which have effect on flow rate were also considered. The effect of different flow rates on copper alloy corrosion, such as laminar, transition, and turbulent flows, were investigated. It was found that the flow rate condition has a significant effect on the protective copper oxide layer in the inner surface of copper alloy tubes. Surface metallographic characterization by FESM, SEM, and EDX, demonstrated that the copper oxide surface layer cannot withstand the turbulences at the beginning of the turbulent flow condition, while the oxide layer erosion is much less during fully developed turbulent flow condition. Therefore, the corrosion rate values is maximum during the initial phases of the turbulent flow condition, but becomes very low at fully developed turbulent flow conditions associated high water velocity. This indicates that the overall flow rate conditions, which include physical properties of the fluid, hydrodynamic parameters, and dimensions of the pipe, have the dominant influence on corrosion rate.