Friday, Feb 07, 2014 at 13:23
Dingojim, you are quite at
liberty to believe that it works if that's what you need to do, but even a cursory scan of cathodic protection literature will tell you otherwise.
Here is just a short excerpt on the matter from one of my text books.
quote
"Cathodic protection is a method by which the transfer of ions into, rather than out of, the surface of a metal which is in contact with an oxidising agent is ensured by the introduction of another metal (the galvanic or sacrificial anode) into the electrical circuit of the corrosion cycle.
Having a more anodic surface than the metal to be protected, all the current will flow from the introduced anode and so the metal to be protected becomes cathodic in comparison to the anode.
This effectively stops the oxidation reactions on the metal surface by transferring them to the galvanic anode, which will be eroded/sacrificed in favour of the structure under protection.
For this method to be effective there must be a solid electrical connection between the anode and the metal to be protected, and an ion pathway between both the electrolyte (ie. water or moist soil) and the anode, and the electrolyte and the metal to be protected.
This forms the closed circuit for electron flow of:- anode - electrolyte - protected metal - anode;
The process of bolting a piece of active metal such as zinc to a less active metal, such as mild steel, in air (whether moist or not), which is a poor conductor and so does not present a closed circuit, will not furnish any corrosion protection whatsoever".
endquote.
I am aware that you will not wish to accept my word for this so I attempted to find a similar article on the internet for your interest.
One exists on Wikipedia which is almost wordperfect to the above.
Have a look
here, the sentence just above the heading "anode materials" says it all.
Most rust that occurs on a vehicle is the result of localised galvanic cell action which cannot be prevented by either remote cathodic or so called electronic rust protection methods, keeping moisture out by painting, or electroplating are the only ways to achieve corrosion protection on these surfaces
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