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Zinc anodes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


A sacrificial anode is a metallic anode used in cathodic protection where it is intended to be dissolved to protect other metallic components.
The more active metal corrodes first (hence the term "sacrificial") and generally must oxidize nearly completely before the less active metal will corrode, thus acting as a barrier against corrosion for the protected metal.

Anode lead wires shall be a minimum of 3 m in length and shall consist of AWG #12/7 stranded copper wire with type RWU-90 insulation.

Zinc anodes shall be supplied with a white lead wire. The lead wire shall be connected to the core with silver solder or an approved equal.
The connection shall be insulated by filling the recess and any voids in the lead wire core connection with an electrical potting compound. Packaged anodes shall be supplied in a water permeable cardboard tube containing a back-fill mixture of the following composition:

Ground Gypsum - CaSO4.2H2O 75 %
Powdered Bentonite - Al4Si8O20(OH)4NH2O 20 %
Anhydrous Sodium Sulfate - Na2SO4 5 %

Back-fill shall have a grain size so that 100 percent is capable of passing through a #20 (850 µm) screen and 50 percent will be retained by a #100 (150 µm) screen. The mixture shall be firmly packaged around the anode within the permeable cardboard tube by means of adequate vibration.
Cardboard tube size shall be sufficient to provide a minimum thickness of 20 mm of back-fill material between all parts of the anode ingot and the anode packaging.

All anodes shall carry a label identifying the Manufacturer’s name, (Bren Technologies Inc.) type of anode, and the net weight of the anode. Cardboard tubes used to package anodes shall have sufficient strength to permit normal shipping and handling without failure.
Manufacturers of sacrificial anodes shall have their anode chemical composition, current efficiency, and back-fill material tested on a regular basis by an independent testing laboratory to ensure compliance to these Specifications.

The Manufacturer shall furnish, when requested by the Engineer, an "Affidavit of Compliance", and test results prepared by an independent testing laboratory verifying compliance to these Specifications. The back-fill material shall be analyzed using the X-ray diffraction technique for mineral identification or as other approved.

Zinc anodes shall conform to ASTM. B418 Type II (latest edition). Anodes shall have a minimum open circuit potential of –1.10 volts referenced to Cu/CuSO4. Zinc anodes shall have the following composition:

Aluminum 0.005% maximum
Cadmium 0.003% maximum
Iron 0.0014% maximum
Lead 0.003% maximum
Copper 0.002% maximum
Zinc Remainder

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