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Pennies and car batteries

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Oznog

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Awhile back I heard someone saying putting a penny on top of a car battery- like on the plastic- protects the terminals against corrosion.

Now I'm quite familiar with sacrificial anode protection as used to great success in ships and bridges, and galvanized coating. But as I understand it, this requires an electrical connection to the object needing protection, and only protects against liquids which form a continuous contact between the two surfaces.

This isn't a continuous liquid contact scenario, nor is the penny even in electrical contact with the terminal (though it could be). I don't think copper has the high activity level to make an anode versus the lead terminal, but the zinc inside a post-1983 copper clad penny would. Still, the rest of the scenario looks all wrong.

I saw a handful of references in Google to using the penny, yet nobody debunking it. Is this just too obscure a legend to merit a response or could this scenario have some merit to it?
 
copper has an electrode potential of +0.337 for an oxidation reaction with reference to hydrogen and lead has an electrode potential of -0.126. whereas zinc has an electrode potential of -0.763. the lower the voltage the greater the tendency to corrode. so, Oznog you are right, the zinc in the penny might be protecting the lead terminal. but i dont know about the composition of the penny that you use in your country so i cant say anything about that.

if you do get some proof then please share it with us
 
Hmm, so copper alone would actually make lead the anode and corrode it faster (if it did anything)?

Scroll to the pic about halfway down... they're not even touching the terminal:
**broken link removed**

so I'm just not buying this.
 
Perhaps the Mythbusters should get on this and see if it gets busted or not.
:lol:
~Mike
 
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