Corrosion Investigations of Copper Alloys and Cast Stainless Steel Used for Drinking Water Applications

Brass alloys are considered corrosion-resistant in potable water. However, chloride, disinfectants, and high flow rates were reported to weaken pipes, leading to leaks and damage. The degradation of copper alloys causes concern as metal ion release may affect water taste and human health in high concentrations. Therefore, materials with improved flow corrosion properties and increased corrosion resistance are needed. Failure investigations were performed on C52100 brass domestic water flowmeters by visual inspection, microstructural analysis with scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The failure is mostly initiated by high local flow rates causing erosion corrosion attacks with dezincification. The corrosion behavior of C52100 (phosphor bronze), C89520 (Se-Bi brass), and S31600 (stainless steel) was investigated and compared to C27453 (brass) in drinking water with varying contents of chloride, ammonia, and chlorine by potentiodynamic polarization curves and long-term immersion tests. Furthermore, flowmeters (made of C27453 and C89520) were installed in a flow test setup to investigate flow induced conditions in a laboratory environment with aggressive drinking water. Immersion tests, flow tests, and potentiodynamic investigations show that brass corrodes at a higher rate than bronze, Se-Bi brass, and stainless steel in such environments.