Evaluation Of Cathodic Disbonding Of Pipeline Coatings In Sichuan And Chongqing

At present,there are some long-distance pipelines in Sichuan and Chongqing area.In the direct evaluation test of cathodic protection,there are many test piles and even the whole line of power failure is less than-0.85 V.According to the current national standard,the pipeline needs to reach the polarization potential-0.85V to achieve effective protection,so it is necessary to take measures to improve the power cut potential.But in the past to debug the cathodic protection parameters when found,sometimes pipeline electric potential need to mention above-1.50 V,power to make the potential reaches-0.85 V,current biggest electric potential of pipeline cathodic protection regulations in the control within-1.50 V.Papers on cathodic protection electric potential limit research methods at home and abroad and the present situation of each region,the existing pipeline cathodic protection research,through the theoretical analysis of the cathodic stripping mechanism is put forward the influencing factors of cathodic disbonding.At present domestic common cathode protection experiment using electrochemical impedance spectroscopy,scanning Kelvin probe method,through the optimization can reflect most of buried steel pipeline anticorrosion layer evaluation technology and research method of cathodic disbonding,buried steel pipeline in each area of 3 PE and asphalt anticorrosive coating pipeline cathodic disbonding resistance were studied.The sensitive potential of cathodic protection of pipeline in Sichuan and Chongqing and the limit value of pipeline electric potential were obtained through a large number of laboratory tests and field tests.Through the research,it is found that the soil resistivity around the pipeline in Sichuan-Chongqing area is mostly in the range of 20-50?·m(corrosiveness),PH value varies between 4.0-6.1(corrosiveness),salt content is less than 0.05%(corrosiveness weakness)Within a level,no major differences.The only index of soil moisture content in Sichuan and Chongqing varies according to regional differences,ranging from 7-23%.The corrosion level is moderately to moderately strong.For areas with high soil moisture content,more attention should be paid to the evaluation of the cathodic disbondment of the anticorrosive coating to prevent the damage after the anticorrosion coating is peeled off.Combined with indoor simulation test and comparison of field test results,it is found that the maximum values of cathodic protection and power-of potential of petroleum asphalt anticorrosive coating is-2.2V or-1.0V respectively.3PE,heat shrinkable sleeve,heat shrinkable coating with cathodic protection pass,the maximum power-off potential is-3.5V or-1.1V.The comparative analysis of indoor simulation electrification test and field test shows that the main factor affecting the cathodic disbondment of the anticorrosive coating is the anticorrosive defect,followed by the cathodic protection potential,the anticorrosive coating type and the soil moisture content respectively.The success of this research for buried steel pipeline cathodic protection parameters provide guidance and reference for debugging,scientifically to provide technical support for the cathodic protection operation of daily,to improve the management of pipeline cathodic protection,formulate relevant standards has certain theoretical support and application value.