Stress hydrogen-induced

The protection potentials for seawater are described in Section 2.4. In pipelines and harbor installations, there is no limiting negative potential t/ for uncoated earbon steel or for steel provided with thiek eoatings over 1 mm, with yield points up to 800 N mm". With dynamieally highly loaded structures, the protection potential ranges in Table 16-2 should be adhered to as in the regulations [1-3] because of the risk of hydrogen-induced stress corrosion (see Section 2.3.4). 

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. 

In order to develop such design criteria, one needs to study hydrogen-induced fractures in laboratory specimens that simulate the conditions in the fracture process zone in the actual pipeline environment in terms of the stress, strain, and hydrogen accumulation6 1. We have recently demonstrated6-9, that under hydrogen pressures up to 15 MPa both stress and hydrogen fields ahead... 

M. Dadfamia, B. P. Somerday, P. Sofronis, and I. M. Robertson, On the Small Scale Character of the Stress and Hydrogen Concentration Fields at The Tip of an Axial Crack in Steel Pipeline Effect of Hydrogen-Induced Softening on Void Growth, Int. J. Mater. Res., to appear (2008). 

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 ... 

Hydrogen-induced cracking Sulfide stress cracking... 

Stress-oriented hydrogen-induced cracking (SOHIC). 

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