Corrosion Phenomena in Duplex Brasses Containing Aluminium

Grain boundary degradation phenomena in forged CW626N alloy containing aluminium, after exposition to corrosive environment according to standard NS-EN ISO 6509-1:2014, was systematically investigated by scanning/transmission electron microscopes. Already after three minutes exposure to CuCl2 aqueous solution both dezincification and intergranular corrosion were observed in test specimen surface. This indicates that it is practically impossible to consider dezincification with -phase as initiation point as a separate process from the corrosion along the grain boundaries (IGC). The driving force for such fast kinetic along the grain boundaries is the local zones depleted or enriched in less noble alloying elements such as zinc, aluminium and tin. In addition, the complex AlAs particles, also distributed along the grain boundaries, directly decrease the availability of corrosion inhibiting elements. Overall results obtained in this investigation indicate an accelerating effect of aluminium and tin on the corrosion initiation and further propagation along the grain boundaries.