On the pipeline polarization in the case of insulation delamination from its surface


I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Kyiv
Usp. materialozn. 2020, 1:40-45


The cathodic protection parameters for two pipelines with a diameter of 1420 mm were calculated. The protection zone for the first pipeline is 6 km long and for the second one it is 5 km. The cathode station current is 12,9 A for the first pipeline and 4 A for the second one. There are a damage and detachment of pipeline insulation, andconsequently a thin layer of electrolyte is located in the detachment area between the metal surface and the insulation. Almost the entire surface of the pipeline has polarization potential. For the first pipeline, the values of the protection potential at neighboring measurement points change quite dramatically, the difference between them can reach tenths of a volt. The polarization current density at the ends of the protection zone is quite small, and accordingly the polarization potential is close to the corrosion potential. But in the vicinity of the drainage point, these values are much larger. The situation is almost the opposite for the second pipeline, where the cathode station current is 4 A. The current density is almost equally distributed throughout the protection zone, slightly larger at its ends. The polarization potential changes accordingly. Its values are larger than the first case. In the cathodic protection, the potential of the pipeline relative to ground zero is important. Its average value depends on the magnitude of the cathode station current. Its graph intersects the lower part of the protection potential graph in the first case and the middle of the graph in the second. The protection potential is the difference between the potential of the pipeline and the earth surface. In the first case, in the vicinity of the drainage point this difference is much larger inside compared to the ends of the zone. As a conclusion, in the practice of cathodic protection it is important to regulate the value of the cathode station current in order to achieve the optimum protection.

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1. Frantsevych Y.N., Liashenko M.E., Hrymailovskyi V.A. Opyt zashchyty hazoprovoda Dashava-Kyev ot pochvennoi korroziii bluzhdaiushchykh tokov [Experience in protecting of the Dashava-Kiev gas pipeline from soil corrosion and stray currents]. Zashchyta metallov. 1968. No. 5. P. 597-603 [in Russian].

2. Osadchuk S.O., Nyrkova L.I., Rybakov A.O., Lukovych V.V. Doslidzhennia vplyvu katodnoi poliaryzatsii u 3%-nomu rozchyni NaCl na destruktsiiu polimernoho strichkovoho pokryvu u stendovykh umovakh [Study of the effect of cathodic polarization in 3% NaCl solution on the destruction of polymer tape coating under bench conditions]. Matematicheskie modeli i vychyslitelnyi eksperiment v materyalovedenii. Sb. nauch. tr. In-ta probl. materyalovedenyia NAN Ukrainy. 2014. Issue 16. P. 13-19 [in Ukrainian].

3. DSTU 4219-2003 Truboprovody stalevi mahistralni. Zahalni vymohy do zakhystu vid korozii [Steel main pipelines. General requirements for corrosion protection]. Kyiv, 2003. 68 p. [in Ukrainian].

4. Lukovych V.V. Rozrakhunok parametriv katodnoho zakhystu mahistralnoho truboprovodu [Calculation of cathodic protection parameters of the main pipeline]. Preprint of the National Academy of Sciences of Ukraine. Kyiv: In-t probl. materialoznavstva im. I. M. Frantsevycha NAN Ukrainy. 2011. 47 p. (Preprynt NAN Ukrainy) [in Ukrainian].