Although intergranular stress corrosion cracking (IGSCC) of high-pressure gas pipelines has been known for more than 20 years, a transgranular form (TGSCC) was detected more recently. Instances of TGSCC have been associated with dilute solutions with pH values in the region of 6.5 because of the presence of carbon dioxide (CO 2 ). Such pH values indicate relatively little, if any, cathodic current reaches the pipe surface, since hydroxyl ions would be generated and pH would increase to values in the region of 10 if current did reach the pipe surface. Slow strain rate testing (SSRT) of pipeline steel specimens in dilute solutions of pH in the region of 6.5 suggested dissolution and hydrogen (H) ingress into the steel are involved in the crack growth mechanism. The initiation of TGSCC in specimens subjected to cyclic loading and maximum stresses approximating those of an operating line was facilitated by pitting. The geometry of the pits allowed the localized generation of solutions of lower pH than that of the bulk solution outside the pits, thereby facilitating dissolution and H discharge.
A set of straightforward experimental techniques are described for the examination of slow strain rate stress corrosion cracking (SCC) of sheet deforming under nearly all multiaxial deformation conditions which result in sheet thinning. Based on the local fracture strain as a failure criterion, the results contrast the stress corrosion susceptibility in uniaxial tension with those in both plane strain and balanced biaxial tension. As an application of the technique, preliminary results are presented describing the slow strain rate SCC of admiralty brass in an aqueous 0.1 M CuSO4 solution at open circuit potential. These results indicate that the loss of ductility associated with the SCC of the brass increases as the stress state changes from uniaxial toward balanced biaxial tension.
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