When a rectifier type system is used, the current is derived from an outside source and is not generated by the corrosion of a particular metal as is the case with galvanic anodes. However, materials used as energized anodes do corrode. Thus, junk pipe and steel rails that were at one time used extensively as anode materials in rectifier type systems, corrode at the rate of 20 lbs. per ampere year.
Even a relatively small rectifier system, with a capacity of only 10 amperes, would consume 2000 lbs. of steel in 10 years. Therefore, longer life anode materials were sought. The materials that are used almost universally today are graphite, high silicon cast iron and precious metal oxide coated titanium. In underground work, special coke breeze backfills are usually used for the purpose of providing a uniform environment around the anode and for lowering the anode-to-earth resistance.
Source:www.bushman.cc/pdf/corrosion_theory.pdf
Even a relatively small rectifier system, with a capacity of only 10 amperes, would consume 2000 lbs. of steel in 10 years. Therefore, longer life anode materials were sought. The materials that are used almost universally today are graphite, high silicon cast iron and precious metal oxide coated titanium. In underground work, special coke breeze backfills are usually used for the purpose of providing a uniform environment around the anode and for lowering the anode-to-earth resistance.
Source:www.bushman.cc/pdf/corrosion_theory.pdf
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Here in Florida we use platinum anodes. Our basic cathodic protection system follows this general installation procedure:
1. Strip away old concrete. Check for electrical continuity of the rebar/mesh steel. Repair substrate as per standards.
2. Place platinum anodes on the balconies affixed by a mesh tape.
3. Apply conductive anode mastic that covers the anodes.
4. Then apply (let cure!!) layers of protective overcoat – usually a acrylic or urethane.
5. Install silver/silver chloride reference electrodes surrounded by salt to make it a very corrosive area
6. Install/wire junction boxes that contain all the wires from the system.
7. A rectifier that steps down 120 Volts to 6 – 10 Volts is installed.
There are few more details but you get the picture. Voila! Protected balconies and walkways!!
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