Problems and Suggestions in the Resistivity Measurement of the External Anti-Corrosion Coating of Buried Steel Pipelines

The resistivity of the anti-corrosion coating of buried steel pipeline is an important parameter.In recent years，the value of this parameter has been used to evaluate the overall quality of the anti-corrosion coating of in-service or directional drilling pipelines.All the domestic standards regarding the on-site measurement of this parameter and the evaluation of the overall quality of the anti-corrosion coating are established with reference to NACE TM 0102-2002.However，those domestic standards have not explained the concept of "anti-corrosion coating resistivity" clearly and there is confusion with terms related to "anti-corrosion coating resistivity".The reasons for selecting the general method and the attenuation method are not defined clearly for the measurement of the resistivity of anti-corrosion coating in various standards，and the test location of the soil resistance is not specified when the general method is used for the directional drilling crossing pipeline，resulting in differences in the field test results and evaluation conclusions of the resistivity of the anti-corrosion coating outside the same pipeline by various inspection units.In order to clarify the above problems，the concepts related to the resistivity of the anti-corrosion coating were explained firstly，and then the meaning of the resistivity of the anti-corrosion coating was clarified through theoretical analysis and formula derivation.Furthermore，the measurement results of the resistivity of the anti-corrosion coating of 100 directional drilling crossing pipelines were statistically analyzed.Finally，suggestions on the revision of relevant standards were given，with expect to revise the unclear problems in the new version of the standards.