Dissimilar-Metal Corrosion on Water Well Stainless-Steel Riser Pipe: Bexar County, Texas

Abstract A public water well in a major U.S. city was installed in late 2020, to include a dedicated copper electrical grounding ring in soils close to the wellhead. Within three years, the 416 stainless-steel riser pipe was failing due to pitting corrosion attack. A field study showed that the only source of DC current and corrosion was the conductive coupling of copper grounding and the combination of carbon steel and stainless-steel equipment making up the water well assembly. Sequential removal of copper grounding connections to wellhead metal reduced DC current flow to zero. A solution using decoupling devices was implemented to ensure adequate AC grounding while preventing DC current flows outside of a narrow blocking range.