[TheForge] coal or charcoal morph to Evaporust

[James Binnion]

On Jun 24, 2008, at 9:51 PM, Peter Hirst wrote:

> Frosty:  you answered your own question on the phosphoric acid.  
> Nasty stuff in any strength.

It is used in many food products at the appropriate dilution (think  
soft drinks)


>  Not sure it would work in electrolyte bath.  The electrolysis tends  
> to redeposit the iron back onto itself, while the phosphoric acid  
> tends to dissolve the elemental iron.  The chemical action of the  
> acid and the electrlysis are two different reactions.  The sole  
> function of the ion in the bath is to conduct electricity, which in  
> turn exactly reverses what happens in the the creation of ferric  
> oxide -oxidation. Phosphoric acid dissolves the iron itself, which  
> is why its used to etch for other fininsh preps.

The rust dissolving nature of your electrolytic setup is from the  
reduction of the iron oxide (rust) back to iron by the atomic hydrogen  
liberated at the cathode(-) from the electrolysis of the water in your  
electrolyte. If you use an acid like phosphoric in the electrolyte  
solution you will end up dissolving the anode(-) into the electrolyte  
and those ions will then plate out on the workpiece which you really  
don't want them to do. This is the basis for electroplating but your  
electrolyte will not be a very good plating solution and you will end  
up with all kinds of junk firmly attached to your work piece.

James Binnion
jbin at well.com