b.
Electrical resistivity: 72 micro-ohm-centimeter at minus 6.6
degrees C 20 degrees F (maximum).
c.
Physical properties (nominal):
Tensile strength
103.4 MPa 15,000 psi
Compressive strength
689.4 MPa 100,000 psi
Brinell hardness
520
Density
7.0 grams per cubic centimeter
Melting point
1260 degrees C 2300 degrees F
Coefficient of expansion from zero to 100 degrees C 32 to 212 degrees F:
0.0000132 centimeter per degree C 0.00000733 centimeter per degree F.
2.1.2
Aluminum Anodes
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NOTE: Aluminum anodes are used in cases where
annual or frequent replacement is required due to
ice damage, and routine cleaning of the tank makes
it possible to remove any expended or broken pieces
of anode stock from the tank before they accumulate.
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Provide aluminum anodes of the following nominal composition and size as
indicated:
Copper
4.0 percent maximum
Magnesium
0.5 percent maximum
0.5 percent maximum
Aluminum
Remainder
2.1.3
Precious Metal Anodes
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NOTE: At installations where icing conditions exist
and the scaling index of water is less than 20,000
(i.e., low hardness water), the designer should
consider using precious metal anodes, such as
platinized niobium, platinized titanium, or mixed
metal oxide for cathodic protection systems. The
consumption rate of precious metal anodes is less
than that of other relatively non-sacrificial
anodes. However, precious metal anodes are more
vulnerable to damage and loss particularly during
cleaning and reconditioning of the tank.
Selection of the configuration should be left to the
designer of the system. Long, continuous wire from
lengths of precious metal anodes may have an
attenuating effect. This can be overcome by using
parallel feeder cable connected to segmented lengths
of precious metal anodes at intervals. Such
assemblies must be assembled with factory sealed
with tested electrical connections to the anodes.
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Provide [precious metal anodes] [_____] [solid] [composite] [wire] [rod]
[expanded mesh] [ribbon] in form. Anode core shall be [copper] [niobium]
SECTION 13112N
Page 9
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