Investigation and Analysis on Pipeline Corrosion under Protective Coating

With joint protections of coating and cathode, the buried steel pipeline will still be corroded and penetraded on some pipe surfaces。This has been proved by the investigation. The paper points out that the important reason of corrosion in the corrosive cell formed on some pipe surfaces under coating, so that cathodic protection is uneffective because of coating having shielding effect on the cathodic protecting current during corrosion。The key to forming the corrosive cell on pipe surface under coating lies in the quality of rust clearing. Therefore, we shall pay more attention to the rust clearing work of steel pipe.