TP304L stainless steel piping with 0.22-inch (6-mm) thick ER/E316L field weld joints, tape wrapped and buried underground, developed large open cavities in the pipe outside surfaces, primarily in the base metal along the weld crown in less than nine months. Indirect evidence for MIC as the responsible corrosion mechanism is presented. What have been referred to as MIC characteristics in the literature have been reviewed and laboratory diagnostic procedures for MIC identification are discussed.
Keywords: stainless steel, MIC characteristics, rust stains, subsurface cavities, preferential corrosion, dendritic corrosion, tunneling corrosion, faceted appearance, MIC diagnosis