Steel pipelines

Fig. 2-19 Time to failure vs. potential for X70 pipeline steel in pH 5.5 buffer solution containing 150 mg L sulfide ions at various loads, 15°C = -0.53 V...

High-alloy pipeline steels (e.g. austenitic-ferritic or duplex) have been used where the product stream demands materials with better corrosion resistance than carbon steel. In practice the external corrosion resistance of these materials cannot be guaranteed, so cathodic protection is employed to protect areas which may be subject to corrosion. 

Material Challenges Pipeline Steels and Hydrogen Embrittlement.348... 

Hydrogen diffusivity as a function of temperature. The effective diffusivity data of X52 and X65 pipeline steels obtained under gaseous hydrogen charging conditions are compared with the compiled results for the literature. (After Alefeld, G. and Volkl, J. Hydrogen in Metals I—Basic Properties, Springer, New York, 1978.)... 

Stress-strain curves and microstructure from specimens of pipeline steels precharged with high-pressure gaseous hydrogen at 20,000 psi and 100°C for 8 days (a) API X70, (b) API X70/X80 type, and (c) API X70/X80 type. 

From the preceding discussion, it is seen that characterization of hydrogen uptake and embrittlement of pipeline steels in high hydrogen pressure environment is at its initial stage. In particular, there is little data on weld and heat-affected zone. Much more work needs to be done in the forthcoming years. 

Sofronis, F, Robertson, I.M., and Johnson, D.D. Hydrogen embrittlement of pipeline steels Cause and remediation, 2006 Annual Progress Report, ni.A.5, DOE Hydrogen Program, 2006. 

S = specified minimum yield strength, psi, stipulated in the specifications under which the pipe was purchased from the manufacturer or determined in accordance with (c) below. The specified minimum yield strengths of some of the more commonly used pipeline steels whose specifications are incorporated by reference herein are tabulated for convenience in Table IX-1B. 

M. Dadfamia, P. Sofronis, I. M. Robertson, and B. P. Somerday, Hydrogen/Plasticity Interaction at Internal Cracks in Pipeline Steels, Seventh International ASTM/ESIS Symposium on Fatigue and Fracture, Tampa, Florida, USA, November 2007. 

For comparison, the following relationship has been found for an X70 pipeline steel (slow strain rate test using compact tension specimens with the precrack located in the heat-affected zone of a weld) ... 

Figure 2.22 Hydrogen-induced cracking in pipeline steel. (Reprinted with permission from ASM International. All rights reserved www.asminternational.org)...

Absence of interstitial impurities Northern pipelines Steels with low brittle to ductile... 

Hydrogen sulfide damage. One of the most studied failures in practice is that of pipeline steel for the petroleum industry. Figure 6.65 shows a typical cracking failure of this category. 

E. M. Moore, J. J. Warga. Factors Influencing the Hydrogen Cracking Sensitivity of Pipeline Steels. NACE Corrosion/76 Paper 144, Houston, Texas, U.S.A., 1976-03-22/26, and Materials Performance 15(6), 17 (1976). 

NACE Standard TM0284, "Evaluation of Pipeline Steels for Resistance to Stepwise Cracking, NACE, Houston, TX, latest revision. 

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