Chemical composition

Phosphorus and sulphur limits as given in the standards.

The table compares C22 with C276. C22 has more chromium and less molybdenum and tungsten, and very low carbon and silicon to keep welds resistant to intergranular attack.

Mechanical properties

Values for solution-annealed material as given in ASTM B575.

Values for plate to ASTM B575 in the solution-annealed condition. Pipe, bar and forging requirements are similar and are reported on the mill test certificate.

Equivalent designations and specifications

See the grade equivalent chart.

Hastelloy C22 products we supply

• Hastelloy pipes and tubes – B622, B619, B626
• Hastelloy sheets and plates – B575
• Hastelloy round bars – B574
• Hastelloy flanges – B564
• Hastelloy pipe fittings – B366 WPHC22
• Hastelloy fasteners – from B574 bar

All Hastelloy alloys are on the Hastelloy page.

Where Hastelloy C22 is used

Hastelloy C22 is used for chemical and pharmaceutical reactors, heat exchangers and piping handling mixed acids and oxidising chlorides – such as acids contaminated with ferric or cupric ions, chlorine, hypochlorite and chlorine dioxide; pulp and paper bleach plants; flue-gas desulphurisation scrubbers; waste incineration and treatment; pickling and etching; and nuclear fuel reprocessing. ERNiCrMo-10 (C22 filler) is also widely used as a universal filler metal for welding other nickel alloys and super-austenitic stainless steels, because the C22 weld is at least as corrosion resistant as most base metals it joins.

C22 or C276?

Hastelloy C276 is preferred in strongly reducing acids such as hydrochloric acid and in some hot sulphuric acid conditions, where its higher molybdenum and tungsten help. C22 is preferred where oxidising species are present, where conditions alternate, and where better resistance to localised corrosion in oxidising chlorides is needed. Inconel 625 is a lower-cost option for less severe oxidising and seawater service. Corrosion tests in the actual process fluid give the most reliable guide.

Fabrication

Hastelloy C22 is welded with matching ERNiCrMo-10 filler by TIG, MIG and manual arc processes, using low heat input and low interpass temperature to limit the time in the precipitation range. It can be used as welded for most services. It forms well cold, though it work-hardens quickly; hot forming is done in a controlled range and followed by solution annealing and rapid cooling.

Sizes and supply

Hastelloy C22 is supplied in the product forms listed above, in metric and imperial sizes. Because nickel alloys are produced by a limited number of mills and in smaller quantities than stainless steel, availability of each size, the delivery of special sizes and the minimum mill quantities are confirmed with each quotation. Cut lengths, cut plates and machined blanks reduce waste of an expensive alloy and can be supplied on request. Please send the full requirement – grade, specification, product, size, quantity and testing – so that the complete package can be quoted together.

Testing and quality

For critical chemical service, C22 products are often ordered with an intergranular corrosion test to ASTM G28 to confirm correct solution annealing, positive material identification, and ultrasonic testing of plate and bar. Welding procedure qualification for C22 fabrications may also include a corrosion test of the weld. The mill test certificate reports chemistry, mechanical properties and heat treatment for each heat.

Documents and inspection

Material is supplied with mill test certificates (MTC) showing heat number, chemical composition, mechanical properties and heat treatment. Third-party inspection is available on request, and positive material identification can be carried out before dispatch. Because nickel alloys look alike, every piece is marked with grade and heat number for traceability through fabrication.