Failure Analysis on a Buried Flowline in Elevated Temperature and Acidic Soil

A buried carbon steel gas flowline developed an external corrosion after one year operation. It was protected by impressed current cathodic protection and liquid epoxy polymer coating. The root cause analysis revealed that the coal seam oxidation in wet condition generated an aggressive acidic soil environment around the pipe. The coating and cathodic protection at low pH and elevated temperature (90-110 ^ºC) environment was not able to provide adequate protection from external corrosion for this flowline.