A new alloy was introduced recently for applications requiring both corrosion resistance and
high strength. Being a C-type alloy (Ni-Cr-Mo), the new material has excellent resistance to
uniform and localized corrosion in both reducing and oxidizing acids. However, the new alloy
is capable of being age-hardened to effectively double the yield strength over other C-type
alloys. More recently, the new alloy has generated interest in the oil & gas industry due to its
resistance to sour gas environments. A considerable amount of testing has been performed to
support the new alloy in this application. In this paper, the properties of the new alloy relevant
to the oil and gas industry will be presented. These include the NACE standard room
temperature tensile test for sulfide stress cracking and slow strain rate tensile testing at
elevated temperatures (Level VII) both with and without the presence of elemental sulfur. The
alloy has shown excellent resistance in all test conditions. Finally, efforts to develop alternate
processing routes for very high strength applications will be detailed.
Key words: sour gas testing, high-strength, Ni-Cr-Mo, cold work, cold work and aged, C-22HS