Sacrificial Anodes - Magnesium
Aqueous Environment Cast Magnesium Sacrificial Anodes
Protecting Submerged Structures
Applications for the use of magnesium anodes are not limited to structures buried in soil electrolytes. These powerful anodes have proven to be extremely effective at combating corrosion in certain aqueous environments as well. To address these applications, Corrpro manufactures a full line of aqueous magnesium anodes using the
H-1 Grade C alloying standard. The anodes produce an open circuit potential of 1.53-1.55 volts, and are cast into circular, rectangular, square, and teardrop shapes.
Mounting designs on Corrpro's aqueous magnesium anodes were created to address a variety of installation possibilities. Anodes typically associated with condenser applications are constructed with a galvanized steel pipe core for mounting on metal studs. Hull-type anodes, on the other hand, are available with cast-insteel galvanized mounting straps for weld or bolt-on attachment. In addition to these options, the aqueous magnesium anodes can be supplied with a lastisol coating. By employing this special barrier, current output and direction can be controlled, which not only improves the anode's performance, but also extends its life
Typical Applications
Corrpro aqueous magnesium anodes have a variety of fresh- and salt-water applications. These include ship hulls, barges, condensers, heat exchangers, chillers, traveling screens, piers, pilings, and lock and dam tainter and sluice gates. Because magnesium produces a high driving voltage, these types of anodes are also used for rapid polarization of structures in salt-water environments.
Chemical Composition |
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| Element | Content % |
| Al | 5.0-7.0 |
| Mn | 0.15 min. |
| Zn | 2.0-4.0 |
| Si | 0.30 max |
| Cu | 0.10 max |
| Ni | 0.003 max |
| Fe | 0.003 max |
| Other | 0.30 max |
| Magnesium | Remainder |
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| Also available in any other magnesium alloys. | |
Extruded Magnesium Anodes
For Specialized Protection
Magnesium anodes have the highest protection capability of any galvanic material. While these anodes are most commonly used in the cast metal form, certain structures can be better 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 greater amount of current per weight than their cast magnesium counterparts. By supplying more current, extruded anodes can deliver effective protection to structures buried in even highly resistive electrolytes.
Corrpro offers a full line of certified extruded magnesium anodes in both rod and ribbon forms. Certified rod anodes from Corrpro are available in high-potential (1.75-1.77 volts and 1.4-1.5 volts) alloys. They are furnished with a variety of connection options, and are offered in numerous diameters. Corrpro ribbon anodes are manufactured in 3/8" ´ 3/4" flexible coils, which can be easily shaped for use on a multitude of protection projects. The resilient ribbon anode is composed of a high-potential alloy, which produces an open circuit potential of 1.75-1.77 volts. Both the rod and ribbon anodes are constructed with a solid steel core, which runs lengthwise through the anodes for efficient electrical discharge.
Extruded magnesium anodes are most suitable for structures buried or submerged in highresistivity 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. The ribbon anode is used for the protection of pipelines and storage tanks. Extruded anodes are also employed to pre-polarize offshore structures that are to be protected with aluminum anodes.
Chemical Composition |
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| Content % | ||
| Element | 1.75-1.77V | 1.4-1.5V |
| Al | 0.010 max | 2.5-3.5 |
| Mn | 0.5-1.3 | 0.20 min |
| Zn | - | 0.7-1.3 |
| Si | - | 0.05 max |
| Cu | 0.02 max | 0.01 max |
| Ni | 0.001 max | 0.001 max |
| Fe | 0.03 max | 0.002 max |
| Other | 0.30 max | 0.30 max |
| Magnesium | Remainder | Remainder |
|
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H-1 ALLOY CAST MAGNESIUM ANODES
Supplying Cost Effective Protection
Electrolytic conditions in the soil surrounding a buried structure often determine the type of anodes employed in a cathodic protection system. In lowresistivity soil (under 2000 ohm-cm), Corrpro’s H-1 line of magnesium anodes are the most economical choice. Corrpro Certified H-1 anodes are cast to meet American Society for Testing Materials Standard B80, Alloy AZ63. This unique composition allows for even-current output and efficient protection. The anodes are supplied in three quality grades, all of which produce an open circuit potential of 1.53- 1.55 volts.
Special procedures are also employed in the production of the Certified H-1 anodes to ensure long-life performance. Lead wires on all three grades of anodes are silver soldered and then potted with a sealant to prevent the intrusion of moisture.
Typical Applications
H-1 anodes are recommended for use in low-resistivity soils (typically below 2000 ohm-cm). Because the anodes have a lower driving voltage than high-potential anodes, they are ideally suited for structures where over protection is of concern. Their lowercurrent output also allows these anodes to operate longer than their high-potential counterparts in more conductive environments.
Chemical Composition |
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| Content % |
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| Element | Grade A | Grade B | Grade C |
| Al | 5.3-6.7 | 5.3-6.7 | 5.0-7.0 |
| Mn | 0.15 min | 0.15 min | 0.15 min |
| Zn | 2.5-3.5 | 2.5-3.5 | 2.0-4.0 |
| Si | 0.10 max | 0.30 max | 0.30 max |
| Cu | 0.02 max | 0.05 max | 0.10 max |
| Ni | 0.002 max | 0.003 max | 0.003 max |
| Fe | 0.003 max | 0.003 max | 0.003 max |
| Other | 0.30 max | 0.30 max | 0.30 max |
| Magnesium | Remainder | Remainder | Remainder |
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HIGH POTENTIAL CAST MAGNESIUM ANODES
Delivering Superior Protection
Power in galvanic cathodic protection is generated at the anode. With Corrpro's certified line of high-potential anodes, you get the most powerful protection available today. Cast from high-purity magnesium, these anodes produce an open circuit potential of 1.75-1.77 volts, with is 20-3- percent greater than conventional magnesium anodes. This high driving voltage means greater protection can be delivered from fewer anodes. Efficiency of the anode is enhanced even further when installed in a backfill of 75% gypsum, 20% bentonite, and 5% sodium sulfate. This special mixture lowers anode-to-earth resistance, and allows electrical current to flow more easily to the targeted structure.
Corrpro certified high-potential anodes are manufactured according to strict quality control standards. Each production run of high-potential anodes is subjected to capacity, potential, and consumption analysis. This ensures the anodes you purchase will perform as specified.
Typical Applications
High potential anodes can be used to protect most buried metallic structures found in a range of soil resistivities. Because they produce a higher driving voltage than conventional magnesum anodes, they are ideally suited for structures buried in soils with reesistivities in excess of 2,000 ohm-cm, or containing numerous corrosion "hot spots".