【2025 Related Knowledge】Which valves require NACE treatment

The following response is for reference only: The presence of hydrogen sulfide (H2S) and carbon dioxide (CO2) turns natural gas and crude oil into acidic media (Sour Gas; Sour Crude), resulting in stress corrosion cracking (SCC) in the components that come into contact with these fluids.

NACE is the abbreviation for the National Association of Corrosion Engineers, a U.S.-based organization founded in 1943. Due to the expansion of its scope of work and influence, the organization was renamed “NACE®International” in 1993.

NACE provides standards related to metal corrosion in more than 150 different application environments. MR0175/ISO 15156 deals with the use of materials in H₂S-containing oil and gas production, and has been widely adopted by ISO, ANSI, and others, becoming an international standard. MR0103 relates to the use of sulfur cracking (SCC)-resistant materials in corrosive refining environments. These standards cover only corrosion cracking in hydrogen sulfide environments, and do not address general or other types of corrosion.

It is the user’s responsibility to select appropriate instruments and materials for their application in order to comply with NACE standards.

The NACE standards limit the operating temperature, pH value, and chemical composition of many alloy materials, which must be taken into full consideration when selecting materials. Process temperature has a significant impact on the corrosion resistance of the material. For example, when chloride ions are present in the medium, stainless steel becomes particularly sensitive to temperature. The composition and concentration of medium components such as hydrogen sulfide, chlorine, and carbon dioxide are important factors determining the suitability of the material. A low pH value (acidic condition) can lead to the release of hydrogen ions, thereby causing hydrogen embrittlement. Metallographic conditions, such as metal hardened by quenching, are more susceptible to stress fracture than metal after annealing. However, the tensile strength of the annealed metal is slightly lower.

The specifications in the NACE standards are very detailed and complex; it is necessary to take into account the actual process conditions as well as the various factors mentioned above in order to make the right choice. Typically, various materials such as 316 stainless steel, 20 alloy, super duplex steel, Monel, Hastelloy C22/C276, and titanium can be found under different temperature and medium composition conditions.

SSC test standard----NACE TM0177---Laboratory test methods for the resistance of metals to sulfide stress cracking and stress corrosion cracking in H2S environments.

HIC test standard----MACE TM0284---Test method for evaluating the resistance of steels for pipelines and pressure vessels to hydrogen-induced cracking.