Surface degradation of nickel-plated brass fittings

Since many years, brass has been used in many engineering applications given its low production cost, fairly simple manufacture routes and acceptable corrosion resistance. Brass of many different chemical compositions can be found in complex engineering devices such as turbines and bearings or in ornamental and housing applications from which, the fabrication of fittings and connections for plumbing purposes are the most common. In this work, the surface degradation of nickel-plated brass fittings designed for ornamental plumbing purposes was studied using optical and scanning electron microscopy together with energy dispersive and X-ray diffraction analyses. It was found that this phenomenon was caused by the formation of zinc and copper oxides at the metal-coating interface and that reached the surface by means of growing through cracks that were also formed in the nickel coating. The occurrence of these defects is explained in terms of the cleanness of both, the brass specimens and the electrolytic solution used for plating.