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Applying Microelectrodes to Investigate Aged Ductile Iron and Copper Coupon Reactivity during Free Chlorine Application
Citation:
Liggett, J., B. Gonzalez, D. Lytle, J. Pressman, D. Dionysiou, W. Lee, S. Harmon, AND D. Wahman. Applying Microelectrodes to Investigate Aged Ductile Iron and Copper Coupon Reactivity during Free Chlorine Application. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 253:121324, (2024). https://doi.org/10.1016/j.watres.2024.121324
Impact/Purpose:
The environmental or health problem addressed by the study: Corrosion of metals in drinking water distribution system pipe materials. A general description of the work and results: Experiments have been conducted to evaluate the ability of microelectrodes to assess the reaction kinetics of free chlorine and dissolved oxygen at the surfaces of aged ductile iron and copper coupons. The long-term importance or significance of the findings: Provides a new methodology to assess reactivity of pipe surfaces. Who would be interested in or could apply the results (e.g. program or regional partners, general public, local communities): Researchers trying to understand oxidant reactivity of pipe surfaces.
Description:
In drinking water distribution systems, including premise plumbing, dissolved oxygen (DO) and free chlorine (FC) are common oxidants and ductile iron (DI) and copper (Cu) are commonly used pipe materials. Microelectrodes are a tool that have been applied in previous corrosion research and were used in this study to further support microelectrode use to collect quantifiable data to understand DO and FC reactivity and pH changes at the water-metal interface. Using microelectrodes, pH, DO, and FC profiles from the bulk water to near and at the surface of aged DI (154–190 d) and Cu (2 d and 86–156 d) coupons were investigated during periods of flow and stagnation (30 min). Using the measured microelectrode profiles, oxidant fluxes and apparent surface reaction rate, constants were calculated to elucidate differences between DO and FC reactivity with the coupons. Microelectrodes were successfully applied to measure pH, DO, and FC profiles from the bulk water to near aged DI and Cu coupon surfaces; Cu coupons aged quickly and exhibited less reactivity at 2 d with DO and FC than aged DI coupons did after 154–190 d; and for the aged DI coupon experiments, orthophosphate presence stabilized pH profiles where without orthophosphate pH fluctuations of greater than 2 pH units occurred from the bulk water to the DI coupon surface.
URLs/Downloads:
DOI: Applying Microelectrodes to Investigate Aged Ductile Iron and Copper Coupon Reactivity during Free Chlorine Application