Dissimilar-Metal Corrosion on Water Well Stainless Steel Riser Pipe

Paper ID: C2025-00191 ABSTRACT: A public water well in a major U. S. city was installed in late 2020, to include a dedicated copper grounding ring in soils close to the wellhead. Within three years, the riser pipe metal, made of 416 stainless steel, was failing due to pitting corrosion. A field study showed that the only source of the 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. Removal of all copper grounding bonds, one by one, showed the DC current flow reducing to zero. A solution was designed, installed and tested using decoupling devices, to allow continuous AC current flows to ground and to prevent DC current flows inside of a narrow blocking range.