Sacrificial Anodes - ZINC
HULL, BALLAST TANK AND CONDENSOR CAST ZINC ANODES
Protection for Marine Environments
Stopping corrosion begins with selecting an appropriate protection material. On many marine type structures, this material is zinc. To address the demand for this protective material, Corrpro manufactures hull, ballast tank, and condenser zinc anodes for use on structures in brackish and saltwater environments. The anodes are cast using 99.99%-pure high-grade zinc, and are alloyed to meet military specification MIL-A-19001 and the ASTM-B-418, Type I chemical composition standard. Through the addition of nominal percentages of aluminum and cadmium, Corrpro zinc anodes are resistant to the formation of zinc hydroxide around the anode surface, which restricts current flow and can shorten anode life. Their unique composition also allows for a current capacity of 354 amp.-hrs./lb., and an open current voltage of 1.05 (with respect to an Ag/AgCl reference cell).
All Corrpro marine zinc anodes are manufactured using galvanized steel cores. By galvanizing the cores, a stronger bond is created, thus minimizing the chance for core separation and anode defect. The cores are available in strap, pipe, or rod configurations, allowing numerous mounting possibilities. Other measures taken to ensure quality include the performance of chemical analysis and electrochemical tests.
Typical Applications
Corrpro hull, ballast tank, and condenser anodes are designed for use on ships, vessels, piers, pilings, and other metal structures in brackish and saltwater environments. The use of these anodes should be avoided in areas where temperatures may exceed 140°F, or which contain high alkalinity (above 9.5 pH). This is because zinc is prone to polarity reversal in these areas.
Chemical Composition |
|
| Element | Content % |
| Al | 0.1-0.5 |
| Cd | 0.02-0.07 |
| Fe | 0.005 max |
| Pb | 0.006 max |
| Cu | 0.005 max |
| Zinc | remainder |
| Magnesium | Remainder |
MARINE PIPELINE BRACELET ZINC ANODES
For Reliable Protection
Zinc anodes have a proven track record for delivering long-life protection in marine environments. This is especially true for marine pipelines found in bot fresh and saline mud, where effective protection can be provided by Corrpro's zinc bracelet anodes. These anodes are cast to meet military specification MIL-A-18001. They produce an open circuit voltage of 1.05 (with respect to an Ag/AgCl reference cell), and possess a 90% current capacity. Although zinc has a lower per-pound current capacity (354 amp.-hrs./lb.) than most conventional aluminum anodes, zinc and aluminum bracelet anodes of identical size will deliver very similar protection, due to the fact that zinc is 2.6 times more dense than aluminum. The chemical composition of Corrpro's bracelet anodes also allows for better protection against the formation of pacifying films, which can restrict current flow.
To better address a wide variety of installation possibilities, Corrpro manufactures two types of bracelet anodes: semi-cylindrical and multisegmented. Semi-cylindrical anodes are most often installed on smaller-diameter pipe, while multi-segmented anodes are typically used on larger pipe. Both types are manufactured with welded galvanized steel cores, and are coated on the pipe side of the anode with a coal tar epoxy to enhance performance.
Typical Applications
Corrpro zinc bracelet anodes are designed for use on all types of pipelines in fresh, brackish, and saltwater environments. On pipe installations where a concrete covers is to be employed, square-ended bracelet anodes are recommended for the creation of a plane surface. Tapered anodes should be used on all other pipeline installations to minimize problems with offloading by barge rollers. Zinc anodes should not be used in areas where the temperature may exceed 140ºF.
Chemical Composition |
|
| Element | Content % |
| Al | 0.1-0.5 |
| Cd | 0.02-0.07 |
| Fe | 0.005 max |
| Pb | 0.006 max |
| Cu | 0.005 max |
| Zinc | remainder |
 |
|
PENCIL, SEGMENTED, AND SLAB
CAST ZINC ANODES
For Confined Installation Areas
Corrosion attack is not limited only to those areas on steel structures, which are easily accessible or visible to the naked eye. This destructive process also occurs in tightly confined spaces on submarines, in compartments on small vessels, and in numerous other restricted locations. To combat corrosion in these areas Corrpro manufactures pencil, segmented, and slab zinc anodes. The anodes are made using 99.99% pure high grade zinc, which is custom-blended with nominal amounts of aluminum and cadmium to meet military specification MIL-A-18001. They have been rated to deliver an open circuit voltage of 1.05 (with respect to an Ag/AgCl reference cell), and to furnish 354 amp-hrs/lb.
Corrpro solid and segmented pencil anodes are supplied standard with free-cutting brass retaining plugs, which are resistant to corrosion and allow for easy anode installation and replacement. The segmented anodes are offered in two styles for assembly by either selfcontained galvanized cores or separate stainless steel core rods. Slab zinc anodes offered by Corrpro are cast in both square and circular configurations. They may be purchased with or without pipe bushings and can be supplied with insulating washers.
Typical Applications
The unique design of Corrpro’s pencil, segmented, and slab anodes makes them ideally suited for the protection of structures in numerous aqueous environments. Their use in high-temperature (above 140°F) or high-alkaline (above 9.5 pH) areas should be avoided.
Chemical Composition |
|
| Element | Content % |
| Al | 0.1-0.5 |
| Cd | 0.02-0.07 |
| Fe | 0.005 max |
| Pb | 0.006 max |
| Cu | 0.005 max |
| Zinc | Remainder |
|
|
SOIL AND RIBBON AND CAST EXTRUDED
ZINC ANODES
Effective Protection For Low-Resistivity Environments
Zinc anodes have been used since the 19th century to protect steel structures from corrosion. Today, these anodes are still widely utilized, and have proven to be an effective choice for preventing corrosion in select soils and brackish waters. For these environments, Corrpro offers zinc anodes made to the ASTM B-418, Type II alloy standard. The anodes generate an open-circuit potential of 1.1 volts (with respect to a Cu/CuSO4 reference cell). Made from 99.99% pure high-grade zinc, Corrpro zinc anodes offer a 90% current efficiency, and deliver a current capacity of 335 amp.-hrs./lb. This high-purity composition also assures the anodes are more resistant to pacifying films.
Corrpro zinc anodes are available in both cast and extruded forms. The cast anodes are produced in a variety of weights, and are designed for use in low-resistivity soil environments. These anodes are manufactured with lead wires, and are packaged in a backfill consisting of 75% gypsum, 20% bentonite, and 5% sodium sulfate. Corrpro zinc extruded anodes are produced in diamond-shaped ribbon coils. Their elongated shape allows for lower resistance to earth than conventional zinc anodes, and permits easy installation on a multitude of structures.
Both types of zinc anodes are manufactured according to strict quality control standards.
Each production run of the anodes is subjected to capacity, potential, and consumption analysis. The anodes are also made using galvanized steel cores to assure a strong bond between the anode and core.
Typical Applications
Zinc cast anodes are recommended for use in soils with resistivities below 1,000 ohm-cm. Because these anodes have a driving voltage that is lower than magnesium, they are most effective on well-coated steel structures, which require minimal current output. The packaged anodes are commonly used as grounding cells on electrical motors, panels, and conduits, and across insulators on pipelines to limit dangerously high voltages. The extruded ribbon anode can be used in buried applications, as well as in fresh, brackish, or saltwater environments. Neither type of zinc anode should be used in extremely alkaline (above 9.2 pH), acidic (below 5 pH), or high-temperature (above 140°F) electrolytes.
Chemical Composition |
||
| Element | Content % | |
| MIL-A-18001 (ASTM B-418 Type I) | ASTM B-481 Type II | |
| Al | 0.1-0.5 | 0.005 max |
| Cd | 0.02-0.07 | 0.003 max |
| Fe | 0.005 max | 0.0014 max |
| Pb | 0.006 max | 0.003 max |
| Cu | 0.005 max | 0.002 max |
| Zinc | Remainder | Remainder |
|
||