| The two important methods which can protect pipeline in soil is coating and toapplied cathodic protection to pipeline. There is better effect if the two methods are usedtogether. The aim of this paper is to study the problem of monitor probe and the quality ofpipeline coating, which exist in cathodic protection of pipeline in soil. It is necessary to have a reference electrode that can work well in soil environmentduring monitoring and testing pipeline coat and the effect of cathodic protection. In thisarea, the main job was to manufacture a monitor probe, which can be used in a long time.The abutment material between the bluestone electrode in the probe and soil is plaster.Agar was added in bluestone solution to obtain jells. The leakage of bluestone solutionwas reduced. The long life monitor probe contains bluestone reference electrode and brassauxiliary electrode, which were arranged in proper position. Meanwhile define how toascertain its testing range. The performance of long effect bluestone preference electrode made by ChinaPetroleum Pipeline Department was tested. The temperature coefficient, the resistance,the potential stabilization, the osmosis of the preference electrode was investigated.What's more tested the applicability of the simulate pipeline potential system. When thereference electrode is used in nature environment, there are evidences to confirm itscorrect validity. The pipeline coating quality deteriorated with time during they were used. In orderto evaluate pipeline- coating quality, we tested different status coating by means ofElectrochemical Impedance Spectroscopy (EIS) at cathodic polarization potential. Theresult shows that the C?value of good coatings obtained by EIS can display the differenceof coating quality. At different cathodic polarization potential, the spectroscopes wereinvestigated. Meanwhile, the polarization action of defect coatings were tested and theresults confirmed that EIS had evaluated coating quality well.
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