ASTM B423 / ASME SB423 is the standard specification by ASTM International covering Nickel-Iron-Chromium-Molybdenum-Copper alloy seamless pipe and tube, including UNS N08825 (Incoloy 825) and UNS N08221. The specification covers both cold-worked and hot-finished annealed conditions. Incoloy 825 is the most widely specified nickel alloy pipe for chemical process industries due to its exceptional resistance to sulfuric acid, phosphoric acid, and seawater environments. The titanium stabilization prevents intergranular corrosion in welded joints without post-weld heat treatment.

Zhengzhou Huitong (HT Pipe) supplies ASTM B423 UNS N08825 seamless pipe and tube in hot-finished or cold-worked annealed conditions with full Mill Test Certificates (MTC) per EN 10204 3.1. 

1. Standard Scope & Designation

ASTM B423 covers Nickel-Iron-Chromium-Molybdenum-Copper alloys (UNS N08825 and UNS N08221) in the form of cold-worked and hot-finished seamless pipe and tube for general corrosive service. The standard applies to both inch-pound and SI unit systems, with product analysis tolerances defined in ASTM B829.

2. Grades Covered by ASTM B423

3. Chemical Composition — ASTM B423 Table 1

Values are maximum unless shown as a range. Heat analysis per ASTM B423-11.

Note: Iron is present at approximately 30% in N08825. The high nickel (38–46%) combined with titanium stabilization gives Incoloy 825 its superior stress corrosion cracking resistance in chloride environments compared to standard stainless steels.

4. Mechanical Property Requirements — ASTM B423 Table 2

All values are minimum requirements per ASTM B423-11. Testing per ASTM E 8.

5. Heat Treatment & Conditions

6. Testing & Inspection Requirements

7. Pipe & Tube Dimensions — ASTM B423 Tolerances (per ASTM B829)

ASTM B423 dimensions follow ASME B36.19M for OD/wall schedules. Standard tolerances per ASTM B829 for cold-drawn and hot-finished tube/pipe.

Note: For small-bore instrumentation and heat exchanger tube sizes (1/2"–2"), common wall thicknesses are 0.035", 0.049", 0.065", 0.083", 0.095". Cold-drawn tube tolerances: OD ±0.13 mm; wall ±10–12.5% average. Dimensions per ASME B36.19M (Stainless Steel Pipe) for schedule dimensions.

8. Industries & Applications

9. ASTM B423 vs ASTM B407 vs ASTM B829 — Nickel Alloy Pipe Comparison

10. Related Standards

11. How to Order — Required Information

12. Frequently Asked Questions

Q: Is ASTM B423 Incoloy 825 the same as ASTM B423 UNS N08221?

Both are covered by ASTM B423 but are different alloy variants. UNS N08825 (standard Incoloy 825) has Cr 19.5–23.5%, Mo 2.5–3.5%. UNS N08221 has slightly higher molybdenum (3.0–4.0%) and narrower chromium range (20.0–22.0%), providing improved resistance to reducing acids. For most sulfuric acid and seawater applications, N08825 is the standard specification. N08221 is specified when enhanced resistance to dilute hydrochloric or sulfuric acid is required.

Q: What is the corrosion resistance range of Incoloy 825?

Incoloy 825 per ASTM B423 provides excellent resistance to: sulfuric acid at concentrations up to 60% and temperatures up to approximately 60–80°C; phosphoric acid at all concentrations including wet-process production; nitric acid up to 65%; seawater and brackish water; organic acids (acetic, formic, lactic); and chloride-containing environments where stress corrosion cracking would affect austenitic stainless steels. It has limited resistance to strongly oxidizing acids (concentrated nitric, hydrofluoric acid at high temperatures).

Q: What is the difference between ASTM B423 pipe and ASTM B407 pipe?

ASTM B423 Incoloy 825 contains 2.5–4% molybdenum and 1.5–3% copper, providing superior acid resistance (especially sulfuric acid, seawater, and chloride media). ASTM B407 Incoloy 800 contains no molybdenum or copper but has higher chromium (19–23%) and is optimized for high-temperature oxidation resistance up to 900°C. For chemical processing with acid media, specify B423. For high-temperature furnace or cracker service, specify B407 (Incoloy 800H/HT).

Q: Can ASTM B423 pipe be used for cryogenic service?

Yes. Incoloy 825 maintains good toughness at cryogenic temperatures due to its austenitic (face-centered cubic) microstructure. It is used in LNG facilities and cryogenic processing where temperatures down to approximately -196°C (liquid nitrogen) are encountered. For cryogenic applications, cold-worked annealed N08825 (TS≥586 MPa) is preferred over hot-finished material for better strength and toughness. Impact testing at the specified service temperature should be specified in the purchase order.

Q: Is post-weld heat treatment required for ASTM B423 pipe?

No. Unlike standard stainless steels, Incoloy 825's titanium content (0.6–1.2%) prevents intergranular corrosion in the weld heat-affected zone without PWHT. The titanium preferentially combines with carbon at elevated temperatures, preventing chromium carbide precipitation at grain boundaries. For nuclear Class 1 or severe corrosion-critical service, a post-weld solution annealing treatment at 925–980°C with water quench may be specified, but this is not a standard requirement. Filler metal ERNiFeCr-1 (AWS A5.14) is the preferred matching filler.

Request a Quote — ASTM B423 Incoloy 825 Seamless Pipe & Tube

Zhengzhou Huitong (HT Pipe) supplies ASTM B423 / ASME SB423 UNS N08825 (Incoloy 825) seamless pipe and tube in hot-finished and cold-worked annealed conditions. Full EN 10204 3.1 CMTRs, PMI reports, and competitive lead times for chemical processing, oil & gas, and nuclear applications.