By D. A. Sherman, P.E. and R. A. Nixon, Corrosion Probe, Inc.

Wastewater treatment plant clarifier environments present challenges for selecting construction materials. Coated carbon steel, hot-dip galvanized steel and stainless steel are most commonly specified for new or refurbished clarifier mechanisms, and all have their advantages and disadvantages with regard to achieving the intended design life. This article discusses the corrosive conditions in primary and secondary clarifiers; how various process conditions can affect the corrosion mechanisms; in what situations each of these construction materials is or is not appropriate; and how fabrication quality and other details can affect corrosion resistance....