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Electrolysis on aluminimium/ alloy parts?

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Electrolysis on aluminimium/ alloy parts?

Old 09-03-20, 10:55 AM
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tonyfourdogs
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Electrolysis on aluminimium/ alloy parts?

Ello again

I have done a quick search on this topic, so forgive me if I'm duplicating another thread here, but I couldn't find the info I was looking for. I've decided that electrolysis is the way forward for me when it comes to rust removal. Cheap, cheerful and no horrible chemicals my dogs could accidentally encounter and poison themselves with. For steel parts, it seems very straightforward. But what I can't find the answer to is this: components that are a mix of steel and alloy, e.g. derailleurs. Will electrolysis damage alloys or anodised parts? Is it safe to electrocute my derailleurs?

Thanks
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Old 09-03-20, 03:32 PM
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Well, when you put an electrolyte in contact with two dissimilar metals, one will eat the other. Adding an external EMF source will probably accelerate the process.
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Old 09-03-20, 03:34 PM
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...Depending on which way the current is flowing (between the two metals), you might also weld them together.
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Old 09-03-20, 04:07 PM
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are you going to rainbow anodize it so it comes out like the oil slick color?
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Old 09-03-20, 05:13 PM
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This has been hashed and re-hashed in the marine field forever. There is a galvanic table. All metals are on it. Electric flow caused by the dissimilar galvanic property and the presence of an electrolyte means ions travel from the "lesser" metal to the more noble metal. See the table on https://en.wikipedia.org/wiki/Galvanic_corrosion. (Actually, search further for more complete tables. You will see steels and stainless steel over a wide range, What alloy you are talking about matters.

OP, it sounds like you are willing to do an experiment as to what items on your bike will go away when you apply electricity and electrolyte. Those of us who have sailed salt water find that heeding the wisdom of those before is often far less costly. Just for fun, the classic and revered Campy NR rear derailleur had aluminum, at least one steel and brass or bronze in it. Apply galvanic corrosion and one (or more) of those is going away.

I suggest you do this on a bike you care nothing for and report back.

Ben
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Old 09-04-20, 12:19 AM
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haha thanks for your replies folks. I had no idea it would be such a disastrous experiment! Since I now 'know' the outcome, I think I'll save even my most sickly derailleurs the indignity of this cruel curiosity.

It's a good job I asked first, eh?
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Old 09-04-20, 11:19 AM
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I'm not familiar with this proposed method of rust removal, but it does sound a bit like electroplating as a way to add metal to something.....
https://en.wikipedia.org/wiki/Electroplating

.... but it does involve nasty chemicals and other dangerous stuff. Prior to electroplating, you'd have to remove the rust to get down to a conductive surface.

Can't blame you for hoping for a bit of a miracle, though.

Steve in Peoria
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Old 09-04-20, 12:34 PM
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Soak them in Evaporust. That's one of the many great things about it--you can soak pieces, like derailleurs, that contain both steel and aluminum. Unlike oxalic acid or an electrolysis bath, it only reacts with rust.
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