MIL-HDBK-1004/10
High
Standard
Potential
High
Magnesium
Magnesium
Purity
Alloy
Alloy
Zinc
Zinc
For protection of
40,000
96,000
120,000
40,000
well coated structures
For protection of poorly
50,000
120,000
190,000
50,000
coated or bare structures
f
=
anode size factor from Table 3
y
=
structure potential factor from Table 4
p
=
electrolyte resistivity in ohms-cm
The number of anodes is then determined by dividing the total
current required by the output per anode. The expected anode life is
estimated based upon the practical deterioration rate for the selected anode
material. Magnesium is consumed at a typical rate of 17 pounds per ampere
year (lbs/A yr), zinc at 26 lbs/A yr, and typical aluminum alloy anodes at 11
lbs/A yr. As the actual design is an iterative process, such factors as anode
size or material may be adjusted in order to optimize the system being
designed.
More precise calculations for the design of sacrificial anode
cathodic protection systems are given in Section 7. Examples of typical
designs using both sacrificial anode and impressed current systems are given
in Section 8.
For the
4.2.6
Basic Design Procedure for Impressed Current Systems.
design of impressed current systems three steps are taken.
Total Current Determination. The first step is the same as for
4.2.6.1
sacrificial anode systems, namely the determination of the total current
required either from actual current requirement measurements or by multiplying
a typical current requirement (from Tables 1 or 2) by the surface area of the
structure to be protected.
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