Corrosion of Nickel Aluminium Bronze - Effect of Alloying Elements and pH

摘要

Nickel Aluminium Bronze (Ni-AI Bronze) is a copper alloy with addition of AI, Ni and Fe. Several intermetallic particles precipitate during cooling of the alloy, contributing to a high complexity of both phase distribution and phase composition across the surface. Cu, AI, Ni and Fe have different corrosion potentials and corrosion properties in seawater, and for some of the elements, these properties are sensitive to changes in pH. The corrosion properties and pH sensitivity of Ni-AI Bronze reflect the behavior of its alloying elements, and behave like copper in neutral pH, and as Ni and Al at low pH. The work presented her is mainly focused on the corrosion mechanism at low pH (>4) and the order of which the discontinuous and continuous intermetallic phases dissolve. Further, the phase compositions of each phase, and the area ratio between intermetallic phases and the alpha matrix have been calculated as an average of 20 measurements. The corrosion properties and pH dependency of the alloy is compared to the corresponding properties of the alloying elements. The results suggest that Ni plays a significant role in the corrosion properties of Ni-AI Bronze.