Evaluating Inhibitors for Infrastructure Corrosion Control for a Blended Reverse Osmosis and Ion Exchange Process Water

The U.S. Environmental Protection Agencyís (USEPA) Lead and Copper Rule (LCR) Revisions, which took effect on December 16, 2021, has motivated utilities to study their finished water corrosivity within their distribution systems. The City of Sarasota Utilities Department (City) retained the University of Central Florida, through the Department of Civil, Environmental, and Construction Engineering (UCF) to investigate the existing corrosion conditions and how future changes to their treatment process may affect the corrosion rates found in the system. As part of this work, corrosion test rack loops were monitored by UCF at the Cityís WTP. The purpose of these studies was to monitor existing corrosion conditions using pre-corroded linear polarization resistance probes and traditional metal coupons. The addition several phosphatebased corrosion inhibitors were examined at an orthophosphate dose of 1.6 mg/L, after an initial stabilization period. Post-stabilization, corrosion rates of the copper alloy decreased at varying degrees for the three inhibitor products tested, over 50 percent in some cases. The lead/tin solder tested did not show a statistically significant change in the corrosion rate when exposed to the test condition as compared to the existing condition. To study how the future treatment may affect the corrosion rates, UCF designed a flow-through update to a typical lab-scale metal coupon jar test. This configuration was employed at City WTP for baseline results of their existing conditions and at UCF facilities to examine the corrosion rate and metal concentrations in the proposed future conditions.