2023 Volume 72 Issue 3 Pages 85-92
The effect of phosphorus of copper tubes on the dissolution behavior of the tubes in an ammonia solution was investigated with electrochemical measurements. It was found that the copper starts to dissolve as [Cu（NH3）2]＋ ions first, and that, when the monovalent ion concentration exceeds a certain level, the reaction shifts to a dissolution yielding divalent [Cu（NH3）4]2＋ ions. In the latter reaction, the phosphorus reduces the charge transfer resistance of copper dissolution. Phosphorus is mainly segregated at grain boundaries, from which copper dissolved preferentially. The results suggest that the segregation of phosphorus is a causes of intergranular stress corrosion crack.
