Initial oxidation of brass induced by humidified air

Complementary surface and near-surface analytical techniques have been used to explore a brass (Cu-20Zn) surface before, during, and after exposure in air at 90% relative humidity. Volta potential variations along the unexposed surface are attributed to variations in surface composition and resulted in an accelerated localized growth of ZnO and a retarded more uniform growth of an amorphous Cu2O-like oxide. After 3 days the duplex oxide has a total mass of 1.3 μg/cm2, with improved corrosion protective properties compared to the oxides grown on pure Cu or Zn. A schematic model for the duplex oxide growth on brass is presented.

► Microstructure of brass (Cu-20Zn) surface results in Volta potential variations. ► They cause a duplex oxide growth during exposure of brass to humidified air. ► Initial accelerated growth of Zn to ZnO and retarded growth of Cu to Cu2O. ► Improved protective properties of the duplex oxide than of the oxides on Cu or Zn. ► A schematic model for the duplex oxide growth on brass is presented.