UFC 3-570-06
JANUARY 31 2003
originally installed, unless the entire anode system is replaced. Anodes of the incorrect
type could lead to insufficient protection.
The electrical potential of zinc anodes is approximately -1.10 volts DC to
copper/copper sulfate in soil. In some fresh waters, the potential can reverse at
temperatures above 58.3 C (140 F); consequently, zinc should not be used in those
cases. The consumption rate for zinc is 10.6 kilograms (23.5 pounds) per amp year.
The efficiency is greater for zinc than magnesium. For design purposes, the efficiency
of zinc is 90 percent.
Table 2-6. Compositions of Zinc Anodes
ELEMENT
STANDARD
SEAWATER
ALLOY
ALLOY
Aluminum
0.005% max
0.10% - 0.50%
Cadmium
0.003% max
0.03% - 0.15%
Iron
0.00014% max
0.005% max
Lead
0.003% max
0.006% max
Copper
-
0.005% max
Silicon
-
0.125% max
Zinc
Remainder
Remainder
NOTES:
Standard Alloy, Specification ASTM B148-97, Type II
Seawater Alloy, Specification ASTM B148-97, Type I; or
2-32
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