Corrosion Resistant Super Alloys
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When 316L is not enough: what a nickel super alloy like Hastelloy C-22 buys you, and what it costs.
Hastelloy C-22 against 316L
| Hastelloy C-22 | 316L stainless | |
|---|---|---|
| Nickel | 56 percent | 14 percent |
| Chromium | 22 percent | 18 percent |
| Molybdenum | 13 percent | 3 percent |
| Critical pitting temperature, acidified 6 percent ferric chloride | Above 150°C (above 300°F) | 15°C (59°F) |
C-22 is used when 316L is not sufficient and intermediate alloys such as AL-6XN have reached their limit. Like 316L it is ductile, weldable and can be fabricated into industrial systems, at a substantially higher price.
What you get
- More mechanical strength and resistance to thermal deformation.
- Far better resistance to pitting and crevice corrosion in harsh chemistry.
- Less maintenance in aggressive environments.
For hydrocarbon extraction, 304 and 316 stainless are fully compatible with butane, propane and the common cleaning solvents, and a super alloy is rarely justified. It earns its price in acidic, chloride-heavy or high temperature process chemistry. See Stainless Steel: 304, 316 and 316L for the standard grades, and call the shop if your process is outside them.
Sources. Haynes International, Hastelloy C-22 Alloy brochure; Bell, T., Properties of Type 316 and 316L Stainless Steels, ThoughtCo (2020); Paulonis, Oblak et al., Metallurgical and Materials Transactions B (1969).