Chromium handles oxidizing corrosion. Molybdenum handles reducing corrosion. Most nickel alloys lean hard toward one or the other, and Hastelloy C22 is one of the few built to be strong at both, with enough chromium, 20 to 22.5%, to hold up in oxidizing media like ferric chloride and wet chlorine, on top of the molybdenum that already made the Hastelloy C-series famous for tough reducing-acid service. USA Piping Solution supplies Hastelloy C22, also called Alloy 22, as seamless pipe and tube to ASTM B622 and welded pipe to ASTM B619, all in UNS N06022. If your service is reducing acid specifically, hydrochloric or sulfuric with no oxidizing component, our Hastelloy C276 Tubing page may be the better cost fit.
C22 or C276: Read Your Environment First
The chemistry of what's flowing through the pipe decides this faster than any spec sheet:
| Environment | Better Choice | Why |
|---|---|---|
| Oxidizing (ferric/cupric chloride, wet chlorine, mixed acids with oxidizers, flue gas scrubbers) | C22 | Higher chromium, 20-22.5% vs C276's 14.5-16.5%, carries oxidizing-media resistance C276 doesn't have |
| Reducing (hydrochloric or sulfuric acid, no oxidizing component) | C276 | Higher molybdenum, 15-17% vs C22's 12.5-14.5%, and typically the lower-cost option for straight reducing-acid service |
| Mixed or uncertain chemistry | C22 | Broader all-around resistance makes it the safer default when process chemistry varies or isn't fully characterized |
Genuinely unsure which side your process falls on? Send us the water or process chemistry and we'll help narrow it down alongside your metallurgist.
Welding Without Post-Weld Heat Treatment
Ultra-low carbon, 0.015% max, is what lets C22 go into service right after welding in most applications, the same underlying logic as C276, applied even more tightly. Recommended filler is ERNiCrMo-10, matching wire for GTAW and GMAW. As with any high-nickel alloy, keep heat input controlled and avoid excessive interpass temperature to protect the weld zone's corrosion resistance.
Have a Drawing or Datasheet? Send It Over →
Applications
- Flue Gas Desulfurization Scrubbers: one of C22's signature uses, standing up to the wet-chlorine, oxidizing-chloride environment inside FGD systems.
- Pulp & Paper Bleaching: chlorine-based bleach plant equipment.
- Pharmaceutical Manufacturing: process equipment needing broad, dependable corrosion resistance.
- Pickling Operations: mixed-acid pickling baths with an oxidizing component.
- Chemical Processing: general service where process chemistry isn't fully fixed or characterized.
- Waste Treatment & Incineration: equipment exposed to aggressive, variable combustion byproducts.
Testing, Certification & Availability
Every order ships with mill test certification and full material traceability; see our Quality Policy page for the full testing program we run across all grades. Send us your OD, wall thickness, and length requirement and we'll confirm current availability and lead time.
Related Products
Frequently Asked Questions
Is Hastelloy C22 the same thing as Alloy 22?
Yes. Alloy 22 and Hastelloy C22 both refer to UNS N06022; Hastelloy is Haynes International's trademark, and Alloy 22 is the generic name used industry-wide for the same chemistry.
Why would I choose C22 over C276 if C276 came first?
C22 was developed specifically to cover oxidizing and mixed-acid environments where C276, built around molybdenum for reducing acids, is not the strongest fit. If your process is straight reducing acid, C276 often remains the more economical choice.
Does C22 require post-weld heat treatment?
No, in most applications. Its ultra-low carbon content, 0.015% max, prevents the sensitization that would otherwise require PWHT.
What sizes are available in Hastelloy C22 pipe and tube?
Send us your OD, wall thickness, and length requirement and we'll confirm current mill availability and lead time.