Analysis on Coating Deterioration in Qin-Jing Crude Oil Pipeline

Qinhuangdao—Beijing Crude Oil Pipeline is protected externally with modified petroleum asphalt plus impressed current and local sacrificial anodes. The coating has been gradually degraded due to long time underground burial of over 20 years. Based on site investigation analyzed in details are the causes of coating deterioration: ① poor application quality; ② damages to the prefabricated pipes during installation, transport, store and lowering-in/backfilling; ③ effects of hot oil in pipeline; ④ natural asphalt deterioration with time of burial. The following suggestions are given against coating deterioration; keeping the temperature of pipeline flow below 60℃ to prevent coating from degradation, disbonding and de jacketing; checking the pipeline regularly for leakage; organizing coating replacement whenever necessary; and paying attention to coating application and prefabricated pipes construction. It is pointed out that coal tar enamel, extruded polyethylene and fusion bonded epoxy powder are suitable coating materials in China.