The automotive industry uses many O-Rings in many different compounds. Getting the right O-Ring size and material will be the difference between a working product or a product that will fail prematurely. Below we will be listing each compound often seen being used for automotive O-Rings and their typical automotive applications, as well as uncommon applications we come across that work excellent for our customers.
Buna Nitrile is the most common O-Ring material across all industries. In automotive it is seen a lot where it is in contact with oils below the temperature of 250°F. It is also resistant to automotive antifreeze, straight gasoline (no ethanol or other additives), and transmission fluids.
Limitations for Buna-N in the automotive industry are temperatures over 250°F, ethanol and other fuel additives, and automotive refrigerants for air conditioning. For standard automotive fuels a Viton or Fluorocarbon O-Ring material is the go-to. The compatible material for automotive refrigerants is HNBR (highly saturated nitrile rubber).
Viton, also known as FKM or Fluorocarbon, is one of the most common O-Ring materials in the automotive industry due to its resistant to most fluids involved in automotive applications. It will be resistant to all automotive oils up to a temperature of 400°F, and most automotive fuels.
Limitations for this material are automotive refrigerants, and fuels with a high ethanol content or other other additives. To see if this material would be compatible with your type of fuels you may check the chemical compatibility guide. If Viton is not compatible with your type of fuel, you may upgrade to either Viton extreme ETP or Fluorosilicone.
HNBR, or highly saturated nitrile rubber, is a material similar to Buna-N, but it undergoes a process of being dissolved in a solvent, and then introduced to a catalyst and hydrogen gas to hydrogenate the nitrile. This allows the HNBR compound to be resistant to automotive refrigerants, and type A steering fluid. It also has a slightly higher temperature resistance of 300°F.
EPDM is the only standard compound that is resistant to automotive brake fluids. That makes it a valuable material to the automotive industry, but it is does not work well for much else. EPDM is not recommended for any petroleum based oils or fuels because it will cause significant swelling and consequently fail in your application.
Fluorosilicone is a material that combines the temperature range of silicone and the chemical and fuel resistance of a fluorinated rubber. It is most often seen with aviation fuels and racing fuels. We often see this compound headed to very cold places to replace Viton seals along fuel lines that get too cold for Viton seals. Because of it’s excellent low temperature flexibility, it can seal where no material can.
Fluorosilicone, because it does retain physical properties of silicone, is restricted to static applications only.
Viton Extreme ETP is a compound that is overkill in most automotive applications unless you are using fuels with high alcohol content, or specialty treated fuels. It is a good replacement for a dynamic seal you would normally use fluorosilicone in, but needs to be wear resistant. You may look at the chemical compatibility guide to see if this material is right for you.
If you have any additional questions, or would like to get a quote, feel free to contact us!
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