Microstructural Analysis of Corroded Copper Pipes Used in Water Distribution Network

A network of three copper piping systems has been used to distribute cold, warm and hot waters to a healthcare complex. The pipes have been hard-drawn using phosphorus-oxidized copper grade. However, water leakage from the three pipes has been detected after less than 2 years in service. It is shown that the three pipes have been degraded by pitting corrosion due to the relatively high sulfate-to-chloride ratio in the water. The corrosion product formed at the inner surface of each pipe is found to consist of an outermost discontinuous and non-protective layer of copper oxide followed by an intermediate chloride layer, and an inner sulfate layer forming the major component. It is concluded that the most probable cause of failure is sulfur contamination of water at the source.