Effect of zinc and orthophosphate corrosion inhibitors on cement-based pipes

Many water utilities add zinc orthophosphate to treated water to reduce corrosion of plumbing materials within their distribution systems. The significance of zinc as a corrosion inhibitor was examined in bench-scale tests of concrete corrosion. In waters with low hardness and low alkalinity, zinc orthophosphate provided better corrosion inhibition for concrete or cement-based pipes than either zinc or orthophosphate alone. Addition of orthophosphate alone was beneficial in reducing the amount of scaling in waters with high hardness and high alkalinity.