High Potential Magnesium Anodes for Cathodic Protection with
Standard Ribbon steel Core
Tests on underground propane tanks have shown that smaller anodes
can be effective at controlling corrosion on a well coated tank.
Small anodes are used when the surface area or object to be
protected is small.
They cost less than a larger anode, but cost the same as a large
anode to install. However, it is important to remember that the
life of a small anode is shorter than for a larger one. One of the
more common
A 17 pound magnesium anode can produce 1 amp of d.c. current for 1
year; therefore, if it produced 1/10 amp, it would last 10 years
compared to 3-1/2 years for a 5 pound anode. A 17 pound anode
placed in 1,000 ohm-cm clay would generate 170 M.A. of current and
would last only 6 years. If the clay's resistivity is 2,000 ohm-cm,
it would last 11 years. In 10,000 ohm-cm dry sand, it would last 52
years. A normal current output is under 100 M.A. However, this
engineer has seen the natural current output of a magnesium anode
reach 200 milliamps (M.A.) in wet, alkali rich clay. The current
output is dependent on the resistivity of the soil or backfill in
which the tank is installed. Clay or highly mineralized earth is
very corrosive and has a low soil resistivity value of 1,000 to
2,000 ohm-cm. Conversely, dry sand is not corrosive and would have
a soil resistivity value over 10,000 ohm-cm. In order to calculate
an anode life, one has to measure the soil resistivity, know the
weight of the anode, know the alloy composition of the magnesium
and factor in the loss of magnesium due to self corrosion. Finally,
when an anode is 85% consumed, it becomes too small to be
effective. Because soil conditions change with time, one can hope
for the best but should plan for the worst.
Magnesium anodes come in two alloys. H-1 or AZ-63 is 90% magnesium,
6% aluminum and 3% zinc. The zinc and aluminum lowers the cost of
the anode but it also lowers the driving potential to about -1.55
volts referenced to a copper sulfate electrode. It will perform
well in corrosive soil if the tank is well coated and will last
longer than the high potential alloy. The other alloy is 99% pure
magnesium. It is called a "high potential" anode as its open
circuit potential is as high as -1.80 volts. It works better than
the H-1 alloy anode in dry or resistant earth or where more current
is needed because of a poorly coated tank. The higher potential
forces more current to flow than would from an H-1 alloy anode. It
costs more per pound but in many cases it is worth the extra cost.
| UltraMag Anode Chemistry* |
Aluminum
Manganese
Copper
Silicon
Iron
Nickel
Others each
Magnesium | 0.01% max
0.50 - 1.3%
0.02% max
0.05% max
0.03% max
0.001% max
0.05% max
Remainder |
Contact us now for more details :
Vivian Jiang(Ms.)
International Marketing & Sales Department Manager
-----------------------------------------------
China Hunan High Broad New Material Co.Ltd.
70 Chezhan North Road,Changsha, China 410100
Tel:+86-731-85717705 Fax:+86-731-85716569
Mobile/Whatsapp: +86-139-7488-3816
Email: metal@vip.163.com,vivian@hbnewmaterial.com
Skype: vivian.jjy
