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I had an old tool I was trying to remove rust from using electrolysis. I used a solar panel and chlorinated pool water. I have had a difficult time online finding what the products of the reaction should be. After hours in the sun the water turned to an orange reddish color and then almost green. I had read about doing this with salt water and it producing chlorinated gas, does pool water go through the same reaction?

Thanks & Regards

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    $\begingroup$ Hi, and welcome to Chemistry SE. What voltage are you using, and what does your setup look like? You haven't described what happened to the tool? It would also be interesting to do a control experiment where the tool (or something similarly rust) is simply left in the pool water. $\endgroup$ Jun 11, 2019 at 15:49
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    $\begingroup$ I am using a usb solar panel. 5V at 2.4A. I clipped a usb cable and am using anode and cathode that looks like Allen wrenches and I have them in a plastic cup. It appears like the rust is removed on the tip but on the handles it seems to stay. The tool is for cutting sheet metal, I think it is a mild steel and tip has a bit of a goldish tinge once rust is removed $\endgroup$ Jun 11, 2019 at 22:23

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You remove rust mechanically . You can treat the clean surface with a "conversion" coating ( phosphoric acid + ?) to slow new rust.

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Rust generally consists of hydrated ferric oxides and hydroxides and is a poor conductor of electricity. During rust electrolysis, the water that seeps underneath the bulk rust and comes into contact with the cathode is split, generating bubbles of hydrogen gas as $$\ce{2H2O(\ell) + 2e- -> H2(g) + 2OH-(aq)}$$ that then simply mechanically loosen up and dislodge the bulk rust from the underlying metal (which gave your solution the "orange reddish" color that you noticed after the electrolysis).

I used a solar panel and chlorinated pool water.

Chlorinated pool water is a rather oxidizing environment containing hypochlorites and chlorinated cyanurates, which may inadvertently lead to further corrosion of your tool via $$\ce{2Fe(s) + H2O(\ell) + 3OCl-(aq) -> 2FeO(OH)(s) + 3Cl-(aq)}$$ as well as the formation of chloride-green rust, which likely gave your solution the green color that you noticed a few hours later as well.

I had read about doing this with salt water and it producing chlorinated gas, does pool water go through the same reaction?

Hypochlorites and chlorinated cyanurates may release chlorine gas at the cathode as $$\ce{2H2O(\ell) + 2OCl-(aq) + 2e- -> Cl2(g) + 4OH-(aq)}$$

Saltwater pools can additionally release chlorine gas at the anode as $$\ce{2Cl-(aq) -> Cl2(g) + 2e-}$$

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