UNS N08535 (Alloy 8535 or Alloy 2535) is a high alloy austenitic nickel iron chromium material developed for the sour service in oil and gas production, particularly for the high pressure high temperature (HPHT) wells and acid gas injection (AGI) duty. It is the combination of resistance to hydrogen sulfide, chloride pitting and stress corrosion cracking that roughly 29 to 36.5 percent nickel, 24 to 27 percent chromium and 2.5 to 4 percent molybdenum provides that makes it the stainless steel that surpasses them. The materials are supplied in the solution annealed condition to meet the minimum requirements of ASTM B622 and ASME SB622; minimum requirements are typically above 503 MPa tensile, 214 MPa yield and 40 percent elongation. USA Piping Solution provides N08535 certified to EN 10204 3.1 mill test, complete heat traceability and third party inspection to meet the sour service envelope in the well.
Specifications of UNS 08535 (Alloy 8535) Pipes and Tubes
| Specification | Details |
|---|---|
| Product Name | UNS N08535 (Alloy 8535 / Alloy 2535) Pipes & Tubes |
| UNS Number | UNS N08535 |
| Trade Names | Alloy 2535, Alloy 8535, SM2535, CRA 2535 |
| Governing Standards | ASTM: B622 (Seamless Nickel and Nickel-Iron-Chromium-Molybdenum Alloy Pipe and Tube) ASME: SB622 |
| Manufacturing Type | Seamless (Cold Drawn, Cold Worked, Hot Finished) |
| Product Forms | Seamless Pipe, Seamless Tube, Downhole Tubulars, Heat Exchanger Tubes |
| Outside Diameter | Standard 1/8" NB to 8" NB (Pipe) / 6.0 mm to 76.2 mm OD (Tube); custom sizes per ASTM B622 |
| Wall Thickness | Standard Schedules (SCH 10S to SCH XXS) & Custom Heavy Wall Thicknesses |
| Length | Single Random, Double Random, Cut Lengths (Up to 12 Meters / 40 Feet) |
| Supply Condition | Solution Annealed (standard); Cold Hardened / Cold Worked available for high-strength OCTG |
| Sour Service Compliance | NACE MR0175 / ISO 15156 Part 3 (Type 4c CRA), certified against the stated service envelope (H2S, CO2, and chloride environments) |
| Hardness Limit | ≤90 HRB (≤217 HBW) in Solution Annealed condition; ≤33 HRC (for 110 ksi grade) / ≤35 HRC (for 125 ksi grade) per NACE MR0175 Table A.14 |
| Mandatory Mill Tests | Tensile Testing, Hydrostatic Test or Non-Destructive Electric Test (Eddy Current) per ASTM B622 |
| Additional Testing | Positive Material Identification (PMI), Ultrasonic Testing (UT), Eddy Current, Intergranular Corrosion (IGC) testing per client Inspection & Test Plan (ITP) |
| End Finish | Plain End (PE), Beveled End (BE), Premium / API Threaded Connections |
| Surface Finish | Solution Annealed & Pickled (AP), Bright Annealed (BA) |
| Certification | EN 10204 3.1 Standard Mill Test Certificate (MTC); EN 10204 3.2 Third-Party Inspection with SGS, Bureau Veritas, or TÜV on request |
| Traceability | Stenciled/Marked with Heat Number, Size, Standard, and Grade; fully traceable to raw material melt origin |
| Packaging | Bundles with Plastic End Caps, Export-Worthy Wooden Crates / Wooden Boxes |
Applications and Industrial Uses of UNS 08535 (Alloy 8535) Pipes and Tubes
- Sour Gas (H₂S) Production Systems
- High-Pressure High-Temperature (HPHT) Oil & Gas Wells
- Acid Gas Injection (AGI) Wells
- Downhole Tubular Components
- Well Completion Equipment
- Packers and Subsurface Completion Tools
- Offshore Oil & Gas Production Facilities
- Oilfield Exploration and Production Equipment
Frequently Asked Questions
1. What is UNS N08535 (Alloy 8535)?
UNS N08535 (Alloy 8535) is a high-strength nickel-iron-chromium alloy designed for sour service, HPHT, and acid gas injection applications in the oil and gas industry.
2. Is Alloy 2535 the same as Alloy 8535?
Yes. Alloy 2535 and Alloy 8535 are different trade names for the same material with the UNS designation N08535.
3. Is UNS N08535 suitable for sour service?
Yes. UNS N08535 is specifically engineered to resist hydrogen sulfide (H₂S) environments, making it suitable for sour service applications.
4. Does UNS N08535 meet NACE MR0175 / ISO 15156 requirements?
Yes. UNS N08535 is qualified for use in sour service environments and complies with NACE MR0175 / ISO 15156 requirements.
5. What is the difference between ASTM B622 and ASME SB622?
ASTM B622 and ASME SB-622 are technically equivalent. ASME SB-622 adopts ASTM B622 for ASME Code applications, with only minor differences in marking and certification. Use SB-622 for ASME Code equipment and B622 for other applications.
6. What hardness limit applies to UNS N08535 in sour service?
NACE MR0175/ISO 15156 specifies hardness limits for corrosion-resistant alloys in sour service. UNS N08535 should be supplied in a suitable solution-annealed condition, with hardness verified on the mill test certificate against the project requirements.
7. Can UNS N08535 be used in HPHT oil and gas wells?
Yes. UNS N08535 is developed for high-pressure, high-temperature (HPHT) wells and is widely used in downhole tubulars, well completion equipment, and acid gas injection systems.