Nickel Alloy Selection Tool
Technical comparison: C-276, C-22, Inconel 625, Alloy 825, Monel 400 | Free guide
How to use: Check your application conditions (temperature, media, chloride, H2S, stress), then find the matching scenario below. Each scenario recommends the best alloy with alternatives.
1. Quick Comparison Table
| Alloy | UNS | PREN | Max Temp | H2S | Chloride | Acids | Cost | Key Applications |
|---|
| Hastelloy C-276 | N10276 | 69 | 400C | Excellent | Excellent | Excellent | High | Aggressive HX, chemical, offshore HPHT |
| Hastelloy C-22 | N06022 | 71 | 450C | Excellent | Excellent | Superior | High | Flue gas desulfurization, oxidizing acids |
| Inconel 625 | N06625 | 41 | 650C | Good | Good | Fair | High | Subsea, aerospace, high-temp strength |
| Alloy 825 | N08825 | 31 | 350C | Good | Good | Good | Medium | LNG, oil & gas, sulfuric acid |
| Monel 400 | N04400 | — | 480C | Good | Excellent | Poor | Medium | Seawater, cryogenic, hydrofluoric acid |
| 254SMO | S31254 | 43 | 300C | Fair | Excellent | Fair | Medium | Seawater cooling, pulp & paper |
2. Scenario-Based Selection
Scenario A: Seawater Cooling (Ambient 15-30C)
Conditions: Chloride-rich seawater, ambient temperature, no H2S
- Best choice: 254SMO (S31254) — PREN 43, cost-effective
- Alternative: AL-6XN (N08367) — Better at 40-80C hot seawater
- Overkill: C-276 — Works but 3x cost for no added benefit
- Avoid: 316L — Will pit in 1-2 years in seawater
Scenario B: Hot Seawater / Brine (40-80C)
Conditions: Heated seawater, desalination brine concentrate
- Best choice: AL-6XN (N08367) — PREN 46, stable at 80C
- Alternative: C-276 — If H2S also present
- Marginal: 254SMO — May pit above 60C long-term
Scenario C: Aggressive HPHT Well (H2S + CO2 + Cl-)
Conditions: High pressure high temperature, sour gas, 150-200C
- Best choice: C-276 (N10276) — Handles H2S + CO2 + chlorides
- Alternative: C-22 (N06022) — If oxidizing acids also present
- Marginal: Inconel 625 — Good strength but less corrosion resistance
Scenario D: LNG / Cryogenic Service (-196C)
Conditions: LNG liquefaction, storage, MCHE tubes
- Best choice: Alloy 825 (N08825) — Standard for LNG MCHE tubes
- Alternative: Monel 400 — For storage tanks, valves, fittings
- Overkill: Inconel 625 — Higher cost, no added benefit at -196C
Scenario E: Flue Gas Desulfurization (FGD)
Conditions: Oxidizing acids (sulfuric, nitric), high chloride, wet scrubber
- Best choice: C-22 (N06022) — Superior in oxidizing acids vs C-276
- Alternative: C-276 — Acceptable if reducing conditions also present
- Avoid: 316L, 904L — Will fail rapidly
Scenario F: Hydrofluoric Acid (HF) Service
Conditions: HF production, alkylation units, 20-70C
- Best choice: Monel 400 (N04400) — Industry standard for HF
- Alternative: C-276 — If other acids also present
- Avoid: All stainless steels — Severe attack by HF
3. Cost Comparison (Relative to 316L)
| Alloy | Cost Factor | Notes |
|---|
| 316L | 1.0x | Baseline |
| 904L | 1.8x | Mid-tier corrosion |
| 254SMO | 2.2x | Seawater specialist |
| Alloy 825 | 2.5x | LNG standard |
| Inconel 625 | 3.5x | High-temp strength |
| C-276 | 4.0x | Aggressive environments |
| C-22 | 4.2x | Best oxidizing acid resistance |
Selection Tips
- Don't over-specify — 254SMO beats C-276 for plain seawater at 1/2 the cost
- C-22 > C-276 for oxidizing acids (FGD, nitric)
- C-276 > C-22 for reducing acids + chlorides
- Inconel 625 for strength at temperature, not max corrosion
- Monel 400 only for HF or cryogenic, avoid acids
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