Nickel Alloy Flanges: Inconel, Monel and Hastelloy

Where stainless and duplex grades fall short, nickel based alloys take over. They are expensive materials, used where genuinely needed rather than chosen "to be safe".

Common alloys

In flanges these usually fall under ASTM B564 rather than A182, which matters for ordering and certification.

When they are needed

• Chloride and acidic environments where 316L and duplex suffer pitting or stress corrosion cracking
• Continuous service above 600 °C
• Sea water and brine systems
• Strong acid lines such as HF, HCl and H2SO4

Supply considerations

• Lead time. Rarely available from stock; most items come from production with long delivery.
• Certification. EN 10204 3.1 as a minimum, with 3.2 and PMI in critical service.
• Welding. Alloy specific consumables and a qualified procedure are essential; poor practice reduces corrosion resistance.
• Fasteners. Bolting and gaskets must suit the service; carbon steel studs on an alloy flange create a galvanic problem.
• Cost. Many times that of carbon steel, so using the alloy only on the critical section is a common solution.

Share your service conditions and fluid analysis and we will define the alloy and its alternatives with you: enquiry form. See also duplex stainless flanges.

FAQ

Which standard covers nickel alloy flanges?
Usually ASTM B564, separate from the A182 family that covers stainless forgings.

When is nickel alloy needed instead of duplex?
In strong acids, high temperature and aggressive chloride environments where duplex also falls short.

How long is the lead time?
For non stock items it follows the production programme, so early ordering is recommended.