AWWA JAW65358

Zinc orthophosphate has been used for many years as a corrosion inhibitor without a true understanding of its actual contribution to corrosion control. This study examined whether reduced or nonzinc orthophosphate is as effective as zinc orthophosphate for protection of piping materials. The authors reviewed the literature as well as case studies of utilities that had switched from zinc to nonzinc corrosion inhibitors. Pilot-testing was then conducted at six New Jersey water treatment plants to assess the effect of corrosion inhibitors with and without zinc on new metal coupons. For protection of metal pipes, zinc does not appear to play an important role. Orthophosphoric acid was found to be as effective as zinc orthophosphate for protection of metal piping materials and is less expensive on a phosphate basis. In addition, converting from zinc orthophosphate to a nonzinc alternative translates into less zinc that is released into the environment or must be removed from wastewater. Includes 15 references, tables.