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Page 9a

Material Compatibility

Biodiesel interacts differently with materials than diesel fuel.  Some metals have a catalytic effect on the biodiesel oxidation process.  Contact with these materials should be avoided, particularly for biodiesel in long-term storage.  Copper and copper-containing alloys such as brass and bronze should be avoided.  Lead, tin, and zinc are also cited as having some incompatibility with biodiesel [Tyson, see below].  Aluminum, steel, and stainless steel are acceptable tank materials and stainless steel and black iron are commonly used for piping.  Galvanized and copper pipe should not be used for biodiesel or diesel fuel.  The table below shows the effect of biodiesel on elastomers and polymeric materials.

Table 1.  Material Compatibility with Biodiesel


Material BXX Effect compared to diesel fuel
Teflon B100 Little change
Nylon 6/6 B100 Little change
Nitrile B100 Hardness reduced 20%,
     swell increased 18%
Viton A401-C B100 Little change
Viton GFLT B100 Little change
Fluorosilicon B100 Little change in hardness, swell  
         increased 7%
Polyurethane B100 Little change in hardness, swell  
         increased 6%
Polypropylene B100 Hardness reduced 10%, swell
         increased 8-15%
Polyvinyl B100 Much worse
  B50 Worse
  B40 Worse
  B30 Worse
  B20 Comparable
  B10 Comparable
Tygon B100 Worse
     

 

Table from: Biodiesel Handling and Use Guidelines, K. Shaine Tyson, National Renewable Energy Laboratory, NREL/TP-580-30004, September 2001.  Can be downloaded from:  www.afdc.doe.gov/pdfs/5845.pdf

Note that the tests with polyvinyl show that the impact of biodiesel lessens as the blend level decreases.  Experience has shown that this effect holds for other materials also.  Blends of B20 or less do not seem to cause problems within a reasonable time period.  With higher level blends, users should be aware of the elastomer materials that are used in their diesel engine fuel system.  While most modern diesel engines use steel lines for the entire fuel distribution system, older engines and those repaired with non-OEM parts may contain incompatible materials.  Older pumps may also contain elastomer diaphragms, seals and o-rings.  These are usually made from Viton but if made from Nitrile or natural rubbers will deteriorate from contact with high levels of biodiesel.

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