Influence of Static and Cyclic Tensions on Corrosion - Mechanical Destruction of Steels in Hydrogen Sulfide Environments

Abstract

It has been investigated that influence, in terms of loading and composition of hydrogen sulfide environments, are resistant to corrosion-mechanical destruction of typical steels appointed to marine constructions, gas and oil equipment, and pipelines which are exploited on a marine shelf: steel 20, steels 10CrSiNiCu, 28Cr2M{cyrillic}oVNbCu, 30CrM{cyrillic}o, stainless steel 12Cr21Ni5T{cyrillic}i and steel of 17Mn1Si with the welded joint. It is discovered that the high resistance of steels to sulphide stress corrosion cracking (SSCC) does not guarantee it high endurance in solution of NACE (5 % NaCl + 0.5 % CH3COOH + H2S, sat., r{cyrillic}N{cyrillic}3...4, t = 20 ± 3 °S{cyrillic}) at cyclic tensions: at a symmetric cycle endurance the least resistant to SSCC of steel 20 goes down comparatively with air in ~1.4 times, and more resistant steel 30CrM{cyrillic}o and 12Cr21Ni5T{cyrillic}i - in ~2.6 and 1.9 times, accordingly. An analogical tendency is observed at an asymmetric cycle at amplitude σa{cyrillic} = 0.2σ0.2. In presence of the welded joints asymmetric tensions reduce their resistance destruction in a greater measure, than specimen from basic metal. It has also been established that the addition of 3.5 % solution of marine salt 15 mg/l to H2S does not influence the stress intensity factor of high-strength steel 28Cr2M{cyrillic}oVNbCu. At the repeatedly static loading with frequency f = 1.1 · 10-5 Hz depending on the level of this steel strength, the value of conditional critical stress intensity factors Kscc in this solution goes down on 10-15 %. Thus at the selection of materials for work in hydrogen sulfide environments, it is necessary, except for the generally accepted approaches, for an estimation of high ability to work to take the influence of alternating tensions. © Springer Science+Business Media Dordrecht 2013.