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## [TowerTalk] Guy Anchor Cathodic Protection - Where?

 To: [TowerTalk] Guy Anchor Cathodic Protection - Where? ornitz@tricon.net (Barry L. Ornitz) Sat May 3 20:59:17 2003
 ```Tony, K1KP, asked: > 3. Where can one buy the cathodic protection devices? What > is a good cathode material? Zinc like on boats? Or does it > have to be further down the electroactive series to protect > the zinc galvanization of the guy anchor? Zinc is normally used to protect iron (galvanizing). The only practical materials more anodic to zinc are magnesium and magnesium/aluminum alloys in that order. Earlier, Don Moman, VE6JY, wrote: > A rule of thumb is 1 amp flowing for 1 year will remove 20 > lbs of material. This is a rule best discarded as the mass of material removed is dependent on the molecular weight of the material and the valence electrons of the material. Faraday's Laws of Electrolysis govern the removal of material. One Faraday of electricity flowing will dissolve (or deposit) one gram- equivalent weight of a substance. The gram-equivalent weight is obtained by dividing the gram-atomic weight of the substance divided by the number of valence electrons required per atom. A Faraday is 9.6501E4 ampere-seconds. Rather than go through the math, let me present a table of common materials [use a fixed width font]. Material ounce/amp-hr pounds/amp-year -------- ------------ --------------- Aluminum 0.0118 6.465 Zinc 0.0430 23.559 Iron (valence 3) 0.0245 13.423 Iron (valence 2) 0.0368 20.162 Copper (valence 2) 0.0418 22.901 Copper (valence 1) 0.0836 45.802 Silver 0.1420 77.798 To go back to Tony's question, it is possible to use an active cathodic protection scheme instead of a passive anodic material, i.e. one that uses a controlled voltage to counteract the potential produced by the corroding material. Active systems require frequent checking to stay in control. They can also generate electrical noise. Eastman Chemical Company used active protection in a few areas. Running low- level instrumentation signals in the area often produced quite high noise levels. In a buried pipeline, this noise should not be a problem, but it might in Tony's situation. 73, Dr. Barry L. Ornitz WA4VZQ ornitz@tricon.net ```
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