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