FKM O-Rings (Viton Fluorocarbon)
Premium fluorocarbon sealing for high-temperature, aggressive chemical and fuel system applications where standard elastomers fail.
Overview
FKM (Fluorocarbon Rubber), widely known under the trade name Viton, is the premium engineering elastomer for demanding sealing environments. Its outstanding resistance to high temperatures, aggressive chemicals, fuels and oils makes it the material of choice in aerospace, chemical processing, oil and gas, and automotive applications where NBR would degrade.
FKM O-rings maintain sealing integrity up to +200C in continuous service - roughly 80C higher than standard NBR - and retain flexibility down to -20C. The fluorine content (65-70% by weight) provides exceptional resistance to a broad range of hydrocarbons, chlorinated solvents, aromatic fuels and concentrated chemicals that would rapidly destroy other elastomers.
Available in 60-90 Shore A hardness, FKM is produced in several grades: standard FKM (Type 1), low-temperature FKM (GF grade, to -40C) and base-resistant FKM (GBL grade) for specific chemical environments. Specify your operating conditions and we will recommend the correct FKM grade.
Material Properties
| Temperature Range | -20C to +200C (-4F to +392F) |
| Hardness Range | 60-90 Shore A |
| Tensile Strength | 10-16 MPa |
| Elongation at Break | 150-250% |
| Compression Set (70h/200C) | <=20% |
| Fluorine Content | 65-70% by weight |
| Specific Gravity | 1.80-1.95 |
| Color (standard) | Black or Brown |
Typical Applications
Chemical Processing
Pump and valve seals in aggressive chemical service, solvent-handling equipment and reactor vessel seals
Oil & Gas
Downhole tool seals, wellhead and Christmas tree seals, and sour gas service
Aerospace
Hydraulic system seals, fuel system O-rings and engine component sealing to AMS specifications
Automotive
Fuel injector O-rings, turbocharger seals and high-temperature engine seals
Industrial
High-temperature autoclave seals, heat exchanger seals and steam-adjacent service
Chemical Compatibility Summary
Compatible With
- - Mineral oils and greases
- - Synthetic hydraulic fluids
- - Gasoline and diesel fuels
- - Aromatic hydrocarbons
- - Chlorinated hydrocarbons
Incompatible With
- - Hot water and steam
- - Polar solvents (ketones, esters)
- - Low molecular weight esters
- - Amines
- - Skydrol (phosphate ester hydraulic fluids)
Compare Nearby Materials
Further Reading
FKM vs FFKM
The cost-performance boundary between mainstream fluorocarbon and premium perfluoroelastomer.
Read articleKey Advantages
Superior High-Temperature Performance
Continuous service to +200C with short-term excursions to +230C. FKM retains sealing force and elasticity at temperatures that cause NBR and EPDM to harden and crack.
Broad Chemical Resistance
Resistant to petroleum oils, aromatic and aliphatic fuels, hydraulic fluids, many acids, chlorinated solvents and most industrial chemicals.
Low Gas Permeability
FKM has exceptionally low gas and vapor permeability, making it suitable for containment sealing in chemical and gas systems where diffusion through the seal material is a concern.
Long Service Life
Excellent compression set resistance, ozone resistance and weathering resistance help FKM seals maintain clamping force and sealing efficiency over long service intervals.
Frequently Asked Questions - FKM
What is the difference between FKM and Viton?
Viton is a registered trademark used for a fluorocarbon elastomer product line. FKM is the ISO and ASTM generic material designation. All Viton is FKM, but not all FKM is Viton-branded.
Can FKM O-rings be used with steam?
FKM has limited resistance to steam and hot water. For steam service above 120C, EPDM is usually the better material choice.
What chemicals attack FKM O-rings?
FKM is not resistant to ketones such as acetone and MEK, certain amines, hot concentrated nitric or sulfuric acids, and low-molecular-weight esters.
Is FKM available in low-temperature grades?
Yes. Standard FKM has a low-temperature limit of about -20C, while low-temperature FKM grades can extend service to -40C.
Why are FKM O-rings more expensive than NBR?
FKM compounds use fluorinated raw materials that cost significantly more than standard rubber compounds. The price premium is justified in applications where NBR would fail quickly or require frequent replacement.