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1.888.800.MESA
Magnesium anodes have the highest protection capability of any galvanic material. While these anodes are most commonly used in the cast form, certain structures can be more efficiently protected through the use of extruded magnesium configurations. Extruded magnesium anodes have high surface and length ratios in relation to cross sectional size. This allows these anodes to deliver a higher current per weight than standard cast magnesium anodes. By supplying more current, extruded anodes can deliver effective protection to structures buried in high resistivity soils.
MESA offers a full-line of extruded magnesium anodes in both rod and ribbon forms. Rod anodes are available in an alloy providing 1.4-1.5 volts driving potential (Galvorod). They are furnished with a variety of connection options and offered in numerous diameters. Ribbon anodes are manufactured in 3/8" x 3/4" flexible coils which can be easily shaped for use on a multitude of protection applications. The ribbon anodes are manufactured in a high potential alloy (Galvoline) providing 1.6 - 1.7 volts driving potential.
Both rod and ribbon anodes are manufactured with a solid steel core in the center of the anode. This core distributes current uniformly through the anode to prevent excessive discharge near the connection end.
Galvoline Magnesium Anodes
The conventional GALVOMAG magnesium cast anode is an economical and dependable source of current in soils and waters of comparatively low electrolytic resistivity. However, at higher resistivity's, the problem becomes supplying enough current for protection without installing an excessive weight of anodes.
The Solution? The magnesium ribbon anode called GALVOLINE. A considerable departure from traditional sacrificial anodes, GALVOLINE ribbon anode offers the following advantages:
· Minimum resistance to earth per unit weight of anode installed. The GALVOLINE anode supplies from three to seven times as much current per pound of magnesium installed as does the conventional cast anode, so you get more milliamperes per pound for any weight of anode installed.
· Efficient current distribution along a pipeline reduces current requirements to a minimum. Whereas individual anode installations provide an uneven current distribution along a pipeline, the continuous ribbon anode provides uniform current along the pipeline.
· Fewer electrical connections. The number of electrical connections between anode and the structure being protected is reduced to a minimum. Since the core wire is in contact with each incremental length of anode, the ribbon serves as its own collector wire, elimination much of the wiring normal to the conventional anode installation. Give reasonably uniform corrosion of the anode ribbon and relatively light current drains (1-3mA per running foot), connections made at intervals of 500-1000 feet are adequate. No chemical backfill is necessary.
· Easy mechanical installation. The ribbon is formable enough to permit storage in coils or on reels. If the reel is mounted on a tractor or truck, the ribbon anode can be fed from the reel to a wire laying plow for continuous mechanical installation. The ribbon can also be placed in special configurations such as helical, pancake, or hairpin coils. Where interior surfaces of tanks, large pipes, or condensers are to be protected.
· The nomograph can be used in pipeline applications to determine current output per foot of GALVOLINE and anode life.
Typical Applications
Extruded magnesium anodes are most suitable for structures buried or submerged in high resistivity electrolytes. The rod shaped anodes, with their small diameters, are often used in commercial and industrial water heaters and storage tanks, or driven into the ground to protect gas service risers.
Composition
Anode rods are available as either the standard GALVOROD anode or the high current output GALVOMAG anode. GALVOLINE ribbon anode is manufactured with the high current output composition.
In most environments, the oxidation potential 1.4 to 1.5 volts for GALVOROD and 1.6 to 1.7 volts for GALVOMAG (with respect to a copper-copper sulfate reference electrode). Because of its higher oxidation potential, GALVOMAG anodes of a given size deliver approximately 25% more current (millamperes) than GALVOROD anodes of the same size. As electrolyte resistivity increases, the need for GALVOMAG anodes increases.
Current capacities for GALVOMAG and GALVOROD anodes are similar and will range from 450 to 550 ampere hours per pound, depending primarily on the operating rate (anode current density).
Chemical Composition
Material
Mg %
Al %
Mn %
Zn %
Si % Max
Cu % Max
Ni % Max
Fe % Max
Other Imp. % Max
Each
Total
Galvorod Anode
Bal.
2.5 - 3.5
0.20 min
0.7 - 1.3
0.05
0.01
0.001
0.002
0.30
Galvomag Anode
0.010 max
0.50 - 1.3
-
0.02
0.03
