Cracking hydrogen induced

If the formation of molecular hydrogen is suppressed, nascent atomic hydrogen may diffuse into the interstices of the metal instead of being harmlessly evolved as a gaseous reaction product There are many chemical species which poison this recombination (e.g., cyanides, arsenic, antimony, or selenium compounds). However, the most commonly encountered species is hydrogen sulfide (H S), which is formed in many natural decompositions, and in many petrochemical processes [21]. 

Processes or conditions involving wet hydrogen sulfide, that is, sour services, and the high incidence of sulfide-induced HlC may result in sulfide stress cracking (SSC), which has been a continuing source of trouble in the exploration and exploitation of oil and gas fields, and the subject of many international standards [22]. However, similar problems are encountered wherever wet hydrogen sulfide is encountered (e.g., acid gas scrubbing systems, heavy water plants, and waste water treatment). 

Failures have occurred in the field when storage tank roofs have become saturated with hydrogen by corrosion and then subjected to a surge in pressure, resulting in the brittle failure of circumferential welds. In rare instances, even copper and Monel 400 (N04400) have suffered of HIC. More resistant materials, such as Inconels and Hastelloys often employed to combat HIC, can become susceptible under the combined influence of severe cold work, the presence of hydrogen recombination poisons, and their presence in a galvanic couple with a more anodic metal or alloy. 

The HIC mechanism has not yet fully established. Various factors are believed to contribute to unlocking the lattice of the metal, such as hydrogen pressure at the crack tip, the competition of hydrogen atoms for the lattice-bonding electrons, easier plastic flow of dislocations in the metal at the crack tip in the presence of hydrogen, and the formation of certain metal hydrides in the alloy. 

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Cracking mechanisms in which corrosion is implicated include stress corrosion cracking, corrosion fatigue, hydrogen-induced cracking and liquid metal embrittlement. Purely mechanical forms of cracking such as brittle failure are not considered here. 

Sometimes considered to be a form of hydrogen-induced cracking. 

Hydrogen-induced cracking (HlC) is most commonly encountered in steels but other metals are susceptible, as shown in Table 53.3. The presence of hydrogen atoms in a metal degrades some of its mechanical properties, especially its ductility, leading in some cases to embrittlement. 

Solutions of hydrogen sulfide, because of hydrogen-induced cracking. Grades of steel are available for certain ranges of pH and hydrogen sulfide partial pressure. 

Strength, particularly where the material will be subjected to fatigue loading or is susceptible to degrading mechanisms such as hydrogen-induced cracking ... 

Martensitic type. Heat-affected zone cracking is likely and may be remedied by employing the normal measures required for the control of hydrogen-induced cracking. 

Rowe, M.D., Nelson, T.W., and Lippold, J.C., Hydrogen-induced cracking along the fusion boundary of dissimilar metal welds, Welding Res., February, 1999, p. 31. 

EVALUATION OF THE SUSCEPTIBILITY OF SIMULATED WELDS IN HSLA-100 AND HY-100 STEELS TO HYDROGEN INDUCED CRACKING... 

Evaluation of the Susceptibility of Simulated Welds in HSLA-100 169 and HY-100 Steels to Hydrogen Induced Cracking... 

Figure 19. Dramatic prevention effect introduced by REM additions against disintegration of line pipe steel by hydrogen-induced cracking (HIC)...

RESISTANCE TO HYDROGEN - INDUCED CRACKING IN COMMERCIAL 7"0 SEAMLESS TUBE STEEL... 

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

Environmentally induced cracking consists of (i) stress corrosion cracking (ii) corrosion fatigue and (iii) hydrogen-induced cracking. The general features of these modes of failure are given below ... 

Currently, computer programs for corrosion assessment and control use a combination of expert systems and an object-oriented program such as evaluation of hydrogen-induced cracking of steels,35 or a combination of expert systems and neural networks in corrosion data modeling and prediction.32... 

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