Failure Analysis: Wastewater Drum Bulging

A 55 gallon wastewater drum lid was found to bulge during storage in a remote area. This bulging was of concern because it suggested that the drum was pressurized and that the integrity of the drum could be in question. Drum samples were obtained for analysis. The interior surface of these samples revealed blistering and holes in the epoxy phenolic drum liner and corrosion of the underlying carbon steel drum. It is suspected that osmotic pressure drove permeation of water through the epoxy phenolic coating which was weakened from exposure to low pH water. The permeating water accumulated at weak spots along the coating/carbon steel interface and caused blistering and failure of the coating. The coating failed at locations throughout the drum interior. Subsequent corrosion of the carbon steel released hydrogen which pressurized the drum, thus causing deformation of the drum lid. Additional samples from other wastewater drums on the same pallet were also evaluated, and limited corrosion was visible on the interior surfaces. It is suspected that, with time, the same degradation process would have caused pressurization of the entire batch of sealed drums that contained similar wastewater solutions.