Galvanic Corrosion between Lead and Stainless Steel in Drinking Water Distribution Systems

Lead pipe has been banned for distributing drinking water in Taiwan since 1979. In order to improve drinking water quality, partial replacement of lead pipes, in which lead pipes in the public area were replaced by stainless steel pipes while those in the private premises remained intact, was commonly practiced in Taiwan due to the high cost and difficulties to access private properties. Due to the different potentials of lead and stainless steel, galvanic corrosion may take place if they are electronically connected in water. The objectives of this research are to characterize the effects of galvanic connection between lead and stainless steel on lead release and the effects of pH, chloride and sulfate concentration on this process. The experiments were conducted by connecting aged lead pipes and stainless steel fittings under different pH, chloride to sulfate mass ratio or CSMR and different chloride and sulfate concentration under a fixed CSMR of 2. Orthophosphate was evaluated as a corrosion inhibitor to control lead release. The results demonstrated that lead release increased when lead and stainless steel were galvanically connected and the rate of lead release accelerated with the decreasing pH and increasing CSMR. Orthophosphate could effectively reduce lead release but CSMR needs to be considered since water with a higher CSMR still caused more lead release when galvanic corrosion took place.