This paper contains the discussion of a case history where corrosion attacks took place in a slightly sour waste water disposal pipeline. The exposure of the waste water to the air had taken place from an
open pit, which may have generated elemental sulfur fine particles in the solution. When solids dropped out from the solution, localized attack was detected in the form of underdeposit corrosion. Details are
also given on the laboratory testing results and development of a corrosion inhibition program for such an environment.
Keywords: Iron sulfide, oxygen, waste water pipeline, H2S, LPR, under deposit corrosion