Microelectrode Investigation of Iron and Copper Surfaces Aged in Presence of Monochloramine
Citation:
Gonzalez, B., J. Liggett, D. Lytle, W. Lee, S. Harmon, J. Pressman, AND D. Wahman. Microelectrode Investigation of Iron and Copper Surfaces Aged in Presence of Monochloramine. AWWA Water Science. John Wiley & Sons, Inc., Hoboken, NJ, 6(3):e1375, (2024). https://doi.org/10.1002/aws2.1375
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 monochloramine 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:
Ductile iron and copper coupons were aged 137–189 days and 2 days, respectively, with 2 mg Cl2·L–1 monochloramine under four water chemistries (pH 7 or 9 and 0 or 3 mg·L–1 orthophosphate). Subsequently, microelectrode profiles of monochloramine concentration, oxygen concentration, and pH were measured from the bulk water to near the coupon reactive surface, allowing estimation of flux and apparent surface reaction rate constants for monochloramine and oxygen. Both metals showed similar trends with orthophosphate where orthophosphate decreased metal reactivity with monochloramine (pH 9) and oxygen (pH 7). Comparing iron and copper coupons, apparent surface reaction rate constants for monochloramine and oxygen were one and two orders of magnitude greater, respectively, for iron coupons under all conditions. Overall, this research provides the first insights into monochloramine, oxygen, and pH by direct measurement near ductile iron and copper reactive surfaces aged in the presence of monochloramine.
URLs/Downloads:
DOI: Microelectrode Investigation of Iron and Copper Surfaces Aged in Presence of Monochloramine