Inconel 22 is a nickel-chromium-molybdenum-tungsten corrosion-resistant alloy. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
One of the most versatile nickel-chromium-molybdenum alloys, Inconel 22 was developed in 1985 to achieve better thermal stability than C-276 and better chloride-induced localized-corrosion and stress-corrosion-cracking resistance than C-4. With a balanced content of molybdenum and tungsten, it offers outstanding resistance in both oxidizing and reducing environments: its high chromium content resists oxidizing media such as nitric acid and ferric and cupric chlorides, while its molybdenum and tungsten resist reducing media such as sulfuric and hydrochloric acids. It has exceptional resistance to pitting, crevice corrosion and stress-corrosion cracking, and its low carbon content minimises grain-boundary carbide precipitation during welding, allowing use in the as-welded condition. It is a single-phase, solid-solution alloy supplied in the solution-annealed condition.
Typical applications include chemical and petrochemical processing, flue-gas desulfurisation and pollution control, pulp-and-paper, marine and waste-treatment equipment.
| Property | Value | Unit |
|---|---|---|
| Density | 8.69 | g/cm³ |
| Melting range | 1357–1399 | °C |
| Elastic modulus | 206 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 12.4 | µm/m·°C |
| Thermal conductivity (20 °C) | 10.1 | W/m·K |
| Specific heat (20 °C) | 414 | J/kg·K |
| Structure | Austenitic (FCC), single phase | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | Balance | — | Base element; reducing-media resistance |
| Chromium | Cr | 20.0 | 22.5 | Oxidizing-media / pitting resistance |
| Molybdenum | Mo | 12.5 | 14.5 | Reducing-media / crevice resistance |
| Tungsten | W | 2.50 | 3.50 | Reducing-media resistance |
| Iron | Fe | 2.0 | 6.0 | Residual |
| Cobalt | Co | — | 2.50 | Residual |
| Vanadium | V | — | 0.35 | Residual |
| Carbon | C | — | 0.015 | Low; minimises carbide precipitation |
Solution-annealed condition, typical values for UNS N06022.
| Condition | Property | Value |
|---|---|---|
| Solution annealed | Tensile strength (UTS) | ≥690 MPa (100 ksi) |
| Solution annealed | 0.2% yield strength | ≥310 MPa (45 ksi) |
| Solution annealed | Elongation at break | ≥45 % |
| As-welded | Corrosion resistance | Retained (low carbon) |
| — | Elastic modulus | 206 GPa |
Confirm against the mill test report. The low carbon content preserves corrosion resistance in the weld heat-affected zone.
| Environment | Performance | Notes |
|---|---|---|
| Oxidizing acids (HNO₃, ferric/cupric chloride) | Excellent | High chromium content |
| Reducing acids (H₂SO₄, HCl) | Excellent | Molybdenum + tungsten |
| Pitting / crevice corrosion | Excellent | Superior to stainless steels |
| Stress-corrosion cracking | Excellent | High nickel content |
| Wet chlorine / mixed acids | Excellent | Versatile oxidizing/reducing performance |
The balanced chromium, molybdenum and tungsten content gives outstanding resistance across both oxidizing and reducing environments — including wet chlorine, mixed and contaminated acids, seawater and brines — with exceptional resistance to localized attack, making it suitable for "upset" and multipurpose process conditions.
A single-phase solid-solution alloy; not hardenable by precipitation. Properties are set by solution annealing.
Solution Anneal Solution anneal at approximately 1120 °C (2050 °F) and rapidly quench (water or rapid air cool) to dissolve secondary phases and retain maximum corrosion resistance. The alloy is not strengthened by heat treatment; cold work raises strength.
Excellent weldability; readily welded by the gas-tungsten-arc and gas-metal-arc processes with matching filler, and used in the as-welded condition owing to its low carbon content. No post-weld heat treatment is normally required.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent | Matching C-22 filler (ERNiCrMo-10) |
| GMAW / MIG | Good | Matching filler |
| SMAW / stick | Good | Matching electrode (ENiCrMo-10) |
Weld with matching filler and clean surfaces; the alloy may be used as-welded without post-weld heat treatment.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Difficult; work-hardens, rigid setups, sharp tooling |
| Speeds | Slow speeds, positive feeds, no dwelling |
| Coolant | Ample coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Good; work-hardens, anneal between heavy operations |
| Hot forming | 1010–1175 °C; solution anneal afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Chemical / petrochemical | Reactors, columns, heat exchangers | Oxidizing + reducing acid resistance |
| Pollution control | Flue-gas desulfurisation (FGD) systems | Wet-corrosion + chloride resistance |
| Pulp & paper | Bleaching equipment | Chloride / acid resistance |
| Marine / waste | Components, waste-treatment hardware | Seawater + mixed-media resistance |
| Product Form | ASTM Standard | ASME |
|---|---|---|
| Plate, sheet and strip | ASTM B575 | ASME SB-575 |
| Bar and billet | ASTM B574 | ASME SB-574 |
| Seamless pipe and tube | ASTM B622 | ASME SB-622 |
| Welded pipe and tube | ASTM B619 / B626 | ASME SB-619 |
Nickel-chromium-molybdenum-tungsten corrosion-resistant alloy. UNS N06022.
| Alloy | Cr % | Mo % | W % | Best Used For |
|---|---|---|---|---|
| Inconel 22 | 20–22.5 | 12.5–14.5 | 2.5–3.5 | Versatile Ni-Cr-Mo-W; oxidizing + reducing media, mixed acids |
| Hastelloy C-276 | 14.5–16.5 | 15–17 | 3–4.5 | Reducing-media-oriented Ni-Cr-Mo-W alloy |
| Hastelloy C-4 | 14–18 | 14–17 | — | Thermally stable Ni-Cr-Mo alloy |
| Inconel 625 | 20–23 | 8–10 | — | General Ni-Cr-Mo-Nb corrosion / strength |
| Hastelloy C-2000 | 22–24 | 15–17 | — | Ni-Cr-Mo-Cu; broadest acid resistance |




