Cracking Corrosion of Cathodically Protected Gas Oil Pipes During Long-Term Operation

The paper presents results of corrosion tests of the linear portion of the main pipeline. It is shown that stress corrosion cracking on the outer cathodically protected pipe localize in media containing up to 20 mg/l H2S practically without oxygen. Under these conditions, embrittlement of the tubular steel occurs, and stress corrosion cracking is observed on the outer cathodically protected surface. The kinetics of crack propagation deep into the pipe wall and along the pipe is studied during the operation of gas oil pipelines.

катодно защищаемая поверхность, магистральные газо-нефтепроводы, плотность тока катодной защиты, плотность предельного тока по кислороду, остаточная скорость коррозии, катодный водород, атмосферы Коттрелла, злектролитическое наводороживание, стресс-коррозионные дефек-ты, эффект Ребиндера, cathodically protected surface, main pipeline, current density of cathodic protection, limiting current density by oxygen, corrosion residual velocity, cathodic hydrogen, Cottrell atmosphere, electrolytic hydrogenation, stress corrosion cracking, Rehbinder effect

1. Khizhnyakov V.I. Korrozionnoe rastreskivanie truboprovodov pod napryazheniem pri transporte nefti i gaza [Corrosion cracking of pipelines under voltage in the transport of oil and gas]. Moscow: Kartek Publ., 2013. P. 37. (rus)

2. Khizhnyakov V.I., Trofimova E.V. Prevyshenie toka katodnoi zashchity nad predel'nym po kislorodu – faktor korrozionnogo rastreskivaniya truboprovodov pod napryazheniem [Excess of cathodic protection current over the oxygen limit as stress corrosion cracking factor of pipelines]. Praktika protivokorrozionnoi zashchity. 2009. No. 1. Pp. 57–61. (rus)

3. Vigdorovich V.I. Vliyanie dioksietiltrietilentetramina na potok diffuzii vodoroda cherez stal'- nuyu membranu iz slabokislykh i neitral'nykh khloridnykh rastvorov, soderzhashchikh N2S i SO2 [The effect of dioxyethyltriethylenetetramine on hydrogen diffusion via steel membrane from subacid and neutral chloride solutions containing H2S and CO2]. Zashchita metallov. 2000. V. 36. No. 5. Pp. 541–545. (rus)

4. Horiuti D.T. Toya Khemosorbtsiya vodoroda [Hydrogen сhemosorption]. Solid state surface science. Moscow: Mir Publ., 1972. P. 23. (transl. from Engl.)

5. Basiev K.D., Bigulayev A.A., Kodzaev M.Yu. Mekhano-korrozionnye protsessy v gruntakh i stress-korroziya v magistral'nykh neftegazoprovodakh [Mechanical-corrosion processes in soils and stress corrosion in main pipelines]. Vestnik Vladikavkazskogo nauchnogo tsentra. 2005. V. 5. No. 1. Pp. 47–53. (rus)

6. Kolachev B.A. Vodorodnaya khrupkost' metallov [Hydrogen brittleness of metals]. Moscow: Metallurgia Publ., 1985. P. 72. (rus)

7. Shapovalov V.I. Vliyanie vodoroda na strukturu i svoistva zhelezouglerodistykh splavov [Influence of hydrogen on structure and properties of iron-carbon alloys]. Moscow: Metallurgia Publ., 1982. P. 165. (rus)

8. Khizhnyakov V.I. Zhilin A.V. Opredelenie inkubatsionnogo perioda obrazovaniya defektov KRN na katodno za-shchishchaemoi poverkhnosti podzemnykh stal'nykh truboprovodov [Determination of incubation period for the formation of stress corrosion defects on cathodically protected surface of underground steel pipelines]. Praktika protivokorrozionnoi zashchity. 2009. No. 4. Pp. 44–48. (rus)

9. Khizhnyakov V.I. Novyi kriterii vybora rezhimov katodnoi zashchity podzemnykh stal'nykh truboprovodov [New criteria for selecting cathodic protections for underground steel pipelines]. Praktika protivokorrozionnoi zashchity. 2009. No. 4. Pp. 13–15. (rus)

10. Khizhnyakov V.I. Trofimova E.V. Analiz mekhanizma tokoobrazovaniya pri katodnoi zashchite podzemnykh stal'nykh truboprovodov ot korrozii [Analysis of current formation at cathodic protection of underground steel pipelines]. Praktika protivokorrozionnoi zashchity. 2014. No. 3. Pp. 5–13. (rus)