A failure of an aboveground storage tank occurred due to external corrosion of the tank floor. The liquid asphalt tank operated at elevated temperatures (approximately 177 deg C, or 350 deg F) and had been in service for six years. Cathodic protection (rectifiers) had been installed since start-up of the tank operation. It was noted, however, that some operational problems with the rectifier may have interrupted its protection. Investigation (visual inspection, on-site examination and testing, EDS analysis of scale deposits, and MIC testing of the soil) supported the conclusion that corrosion may have been caused by an interruption in...