Characteristics of iron corrosion scales established under blending of ground, surface, and saline waters and their impacts on iron release in the pipe distribution system

Interior scales on PVC, lined ductile iron (LDI), unlined cast iron (UCI) and galvanized steel (G) were analyzed by XRD, RMS, and XPS after contact with varying water quality for 1 year. FeCO3, α-FeOOH, β-FeOOH, γ-Fe2O3, Fe3O4 were identified as primary UCI corrosion products. No FeCO3 was found on G. The order of Fe release was UCI > G ⩾ LDI > PVC. For UCI, Fe release decreased as % Fe3O4 increased and as % Fe2O3 decreased in scale. Soluble Fe and FeCO3 transformation indicated FeCO3 solid was controlling Fe release. FeCO3 model and pilot data showed Fe increased as alkalinity and pH decreased.