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Magnesium anodes are used for protecting buried pipelines and tanks, heat exchangers and chillers, large gate valves, evaporative condensers, hot water tanks, etc.
They are available in many shapes and sizes as well as either bare ingots or pre-packaged in cotton bags with chemical backfill.
The POLCOR supply the standard H1alloys ASTM AZ63 the efficiency of the alloy it is 50-54%the capacity of them is 1100-1188 Ah/kg and produce an open circuit potential 1,50 to 1,60V (Cupper/Cupper Sulphate electrode)
POLCOR also supply the High Potential alloy. The efficiency of this alloy is 50-58%, the capacity 1100-1280 Ah/kg and the?open circuit potential 1,70 to 1,78V (Cupper/Cupper Sulphate electrode). The chemical composition of these alloys is listed to the following table :
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Alloy Compositions |
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AZ63 |
High Potential |
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Element |
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Aluminum |
5.3 - 6.7 % |
0.01 % |
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Zinc |
2.5 - 3.5 % |
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Manganese (Min) |
0.15 % |
0.50 ?1.30 % |
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Impurities |
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Iron (Max.) |
0.003 % |
0.03 % |
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Nickel (Max.) |
0.002 % |
0.001 % |
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Copper (Max.) |
0.02 % |
0.02 % |
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Silicon (Max.) |
0.10 % |
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Other single (Max.) |
0.05 % |
0.05 % |
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Total Other (Max.) |
0.30 % |
0.30 % |
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Magnesium |
Balance |
Balance |
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Electrochemical properties |
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Capacity |
1200Ah/kg |
1250Ahr/Kg |
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Efficiency |
50-54 % |
50-58 % |
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Closed Circuit potential |
1.5 V |
1.7 V |
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Open circuit potential |
1.6 V |
1.8 V |
POLCOR magnesium anodes can be supplied in a variety of dimension and weights to meet client’s request.
The most common shape of them is Trapezoid “S" type cylindrical “C" type and D shape "D" type.
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“S" shape Mg Sacrificial anodes |
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Type |
Weight (Kg) |
Height A (Inch) |
Width B (Inch) |
Length C (Inch) |
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3S3 |
1,4 |
3 |
3 |
4,5 |
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5S3 |
2,3 |
3 |
3 |
7,5 |
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9S2 |
4,1 |
2 |
2 |
27 |
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9S3 |
4,1 |
3 |
3 |
13,5 |
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17S2 |
7,7 |
2 |
2 |
51 |
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17S3 |
7,7 |
3 |
3 |
25,5 |
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20S2 |
9,1 |
2 |
2 |
60 |
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32S3 |
14,5 |
3 |
3 |
45 |
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32S5 |
14,5 |
5 |
5 |
21 |
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40S3 |
18,1 |
3 |
3 |
60 |
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48S5 |
21,8 |
5 |
5 |
31 |
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60S4 |
27,2 |
4 |
4 |
60 | |
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“C" shape Mg Sacrificial anodes |
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Type |
Weight (Kg) |
Diameter D(mm) |
Length L (Inch) |
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C25 |
2,56 |
75 |
336 |
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C36 |
3,7 |
114 |
202 |
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C41 |
4,2 |
114 |
230 |
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C77 |
7,8 |
11 |
431 |
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C100 |
10,2 |
11 |
560 |
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C145 |
14,7 |
146 |
494 |
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C227 |
22,9 |
178 |
520 |
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C274 |
28,2 |
114 |
1528 | |
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“D"shape Mg Sacrificial anodes |
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Type ? |
Weight ?(Kg) |
Height B (Inch) |
Width ? A (Inch) |
Length C (Inch) |
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9D2 |
4,1 |
3 |
2 |
21 5/8 |
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14D2 |
6,3 |
3 |
2 |
33 1/2 |
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20D2 |
9,1 |
3 |
2 |
47 3/4 |
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9D3 |
4,1 |
3 |
3 |
13 7/8 |
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17D3 |
7,7 |
3 |
3 |
25 1/4 |
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32D5 |
14,5 |
5 |
5 |
19 7/8 |
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48D5 |
21,8 |
5 |
5 |
30 1/8 |
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3,5D3 |
1,5 |
2 |
3 |
7 1/2 |
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5,5D3 |
2,5 |
2 |
3 |
11 4/5 | |
Backfill
Magnesium anodes used in soils require the use of a prepared backfill around the anode for the following reasons:
a. Increase the effective surface area which lowers the anode-to-earth contact resistance.
b. The bentonite clay absorbs and retains moisture.
c. The gypsum provides a uniform, low resistance environment.
d. The sodium sulfate (a depolarizing agent) minimizes pitting attack and oxide film formation.
Today, the standard backfill for magnesium and zinc consists of:
75% Hydrated Gypsum (CuS04+2H20)
20% Bentonite Clay
5% Sodium Sulfate.
The backfill shall be firmly packaged around the anode by means of adequate vibration. Backfill material shall be of sufficient quantity to cover all zinc anode surfaces to a minimum thickness of 25mm.
The standard or pre-packaged anodes supplied with a connecting, 3 meter long, copper wire 1X16 XLPE/PVC unless otherwise specified.
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Magnesium anodes 
