- Published on Monday, 12 March 2012 09:09
- Written by Don Bush
Q: I have a material certified to be compliant with NACE MR0175. Is that material also compliant with NACE MR0103?
A: The short answer is: maybe, maybe not.
NACE MR0175 and NACE MR0103 both cover requirements relating to materials for resistance to sulfide stress cracking in sour applications (i.e., applications involving the presence of H2S and liquid water). NACE MR0175 was initially released in 1975 and has undergone a number of revisions since then. In the 2003 revision, the scope of MR0175 was expanded to include chloride stress corrosion cracking in addition to sulfide stress cracking. Many requirements changed then, and environmental limits, such as temperature restrictions, were added. Shortly thereafter, MR0175 was merged into International Organization for Standards (ISO) 15156 parts 2 and 3, which resulted in additional changes in requirements.
Despite the fact that the only “official” version of NACE MR0175 is NACE MR0175/ISO 15156, people are still using and specifying NACE MR0175-2002 (the last version—before the scope change), and sometimes they also refer to NACE MR0175-2003, the version just prior to the ISO merger. Therefore, the question asked really needs to be clarified to indicate which version of MR0175 was referenced on the material certification.
Even after that clarification is made, the answer to the question is complex and depends on the specific material involved, and whether any welding is involved. Following are some examples of this complexity:
Scenario 1. Assume the material is a carbon steel casting in accordance with ASTM A216 Grade WCC. In this case, the basic material requirements are roughly the same for all of the NACE standards and versions. The heat treatment requirements are identical. The hardness requirement in all the MR0175 variants is 22 HRC maximum. MR0103 does not include a maximum hardness requirement for this material. At this point, it seems like the MR0175-compliant material would also be MR0103-compliant. However, castings almost always contain weld repairs. MR0103 includes very specific welding requirements for carbon steels, specifying that welding is to be performed in accordance with NACE SP0472. The various MR0175 versions include different welding requirements, but none parallel the MR0103 requirements. Therefore, without reviewing the welding processes and procedures for weld repairs in the casting, compliance with MR0103 cannot be verified.
Scenario 2. Assume the material is an ASTM A995 Grade CD3MN casting. This material was never listed in NACE MR0175-2002 so it cannot be certified compliant to that standard. NACE MR0175-2003 and NACE MR0175/ISO 15156 both require the material to be solution-heat-treated and to contain 35 to 65 volume percent ferrite in the base metal. There is no maximum hardness requirement—both require the ferrite content in the weld deposit to be 30 to 70 volume percent. NACE MR0103 also requires 35 to 65 volume percent ferrite in the base metal. However, it also imposes a maximum hardness requirement of 28 HRC, requires weld deposits and heat-affected zones to contain 35 to 65 volume percent ferrite and requires a Vickers hardness survey to be performed as a part of the welding procedure qualification. Therefore, simply meeting either NACE MR0175-2003 or NACE MR0175/ISO 15156 does not guarantee compliance with NACE MR0103.
Scenario 3. Assume the certification is for an ASTM A105 NPS 4 Class 300 weld-neck flange. ASTM A105 allows this flange to be delivered in the as-hot-forged condition, with no subsequent heat treatment. All of the versions of NACE MR0175 specifically allow ASTM A105 forgings provided they meet a 187 HBW maximum hardness requirement, which is the standard maximum hardness requirement listed in ASTM A105. In other words, all versions of NACE MR0175 provide a specific waiver of the standard carbon steel heat treatment requirements for ASTM A105 material. However, NACE MR0103 does not include this specific waiver for ASTM A105 material. NACE MR0103 requires the material be subsequently heat-treated by annealing, normalizing, normalizing and tempering, or quenching and tempering. Therefore, without further information about the heat-treatment condition, conformance with NACE MR0103 cannot be verified.
Scenario 4. Let’s turn this issue around: Assume an ASTM A351 Grade CF8M casting is certified to be compliant with NACE MR0103. In this case, the base material requirements for all of the NACE MR0175 variants and MR0103 are identical. However, NACE MR0175/ISO 15156 requires that all welding be performed using a procedure that includes a Vickers hardness survey as part of the procedure qualification. NACE MR0175-2002 and 2003 and NACE MR0103 do not include this requirement. Therefore, a CF8M casting produced and weld-repaired in compliance with NACE MR0103 is also compliant with NACE MR0175-2002 and 2003, but is not necessarily compliant with NACE MR0175/ISO 15156. One would need to review the welding procedure used for repairs to see if it included the required Vickers hardness survey before compliance with NACE MR0175/ISO 15156 can be verified.
As this answer shows, there are no simple rules for determining the compliance of a material with one NACE standard based on its compliance with another one. The standards are similar in many ways, but they contain many requirements that do not coincide. Therefore, each must be considered individually to determine compliance.