Supermartensitic stainless steels (SMSS) have high strength and good resistance to corrosion in produced fluids containing CO2 and are cheaper than other competing corrosion resistant alloys. Hence, they are attractive flowline materials and they have been successfully used in a number of offshore applications. Nevertheless, service failures have occurred and two failure mechanisms in particular have caused difficulties at welds: (i) hydrogen embrittlement/ hydrogen induced stress cracking resulting from hydrogen picked-up under cathodic protection and (ii) intergranular stress corrosion cracking (IGSCC). This paper presents experimental data on each of these two failure phenomena and gives details of the currently available ways of avoiding these problems, highlighting where further information is required.

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