NACE MR 0175/ISO 15156 for Corrosion Resistant Alloys for Sulphide Service
NACE MR 0175/ISO 15156 is a Materials Standard issued by the National Association of Corrosion Engineers.
It is originally a US standard intended to assess the suitability of materials for oilfield equipment where sulphide (sulphide) stress corrosion cracking may be a risk in hydrogen sulphide (sour) environments. However, the world standards body ISO has issued it under its own "brand". The latest edition includes technical corrigenda from 2005. Discussions about the standard can be found on the NACE website.
The standard specifies the types of corrosion resistant materials including stainless steels that can be used in specific oilfield environments and places limits on the hardness of the material. This applies both to parent and weld material. The maximum hardness is usually defined in terms of the Rockwell 'C' scale.
No conversion to other hardness scales is given in MR 0175 which presents one problem as softened stainless steels hardnesses are measured using either the Rockwell 'B', Vickers or Brinell scales.
Approximate conversions are available.
A wide range of materials is covered by the standard including most types (families) of stainless steels. The table below shows some of these grades. However, this summary is intended to only give a general idea of this complex standard and is not a substitute for the original document.