Comparison of the spontaneous and anodic processes during dissolution of brass

Thr results of investigations on spontaneous dissolution of alpha, beta', gamma and epsilon -brasses in non-complexing, oxidant free acid solutions (2.0 M H2SO4) have been compared with literature results of anodic dissolution of these alloys. In anodic process the Cu-enriched intermediate phases are created while during spontaneous process dezincification leads to the creation of a layer of pure copper. Occurrence of Cu-rich intermediate phases has not been seen during spontaneous dissolution of beta' and gamma -brasses. As a result of a consecutive reaction, however. copper hydride is created. It appears that the spontaneous dissolution of brasses is related to the mechanism of creation and growth of a new copper phase. It seems that the main difference between those two processes consists in the appearance of hydrogen ions reduction, which is absent during anodic dissolution. It has been suggested, that reduction of the hydrogen ions is responsible for the change of the mechanism, of brass dissolution, from the anodic to spontaneous one. (C) 2001 Elsevier Science Ltd. All rights reserved.