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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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