Monday, July 7, 2014

How to electropolish aluminum

I show a basic electropolishing technique that requires no special equipment and has proven to work well on aluminum (aluminium).


  1. Great stuff, I will give it a try!

    Have you looked at stainless steel cathodes and whether there's a possibility of generating hexavalent chromium in the process? I've come across a lot of conflicting information on the web about the safety of electrolysis when stainless steel is involved, but have steered clear out of an abundance of caution.

    I came across a recipe for electropolishing in the book "Building Scientific Apparatus" which calls for a copper cathode. It was specifically for polishing stainless, though -- 50 parts citric acid, 15 parts sulfuric acid, 35 parts water (all by volume), at 90 celcius and 100mA/sq cm at around 6-12V.

  2. Brian, I'm pretty certain that home/hobby electropolishing will not produce any significant amount of chromium. The phosphorous compounds that will be formed by dumping the acid into the drain will probably be a bigger hazard if you plan to dispose of the acid in that way. Many municipalities have a local "household hazardous waste" collection center where they will accept acids and dispose properly.

    Thanks for the recipe!

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  5. Great video
    I am chemically etching graphics into 5005 allloy with NaOH
    I am using black matt anodised stock predominantly which when it is etched has a matt appearance. The panels look great but could be better with glossy graphics.
    I figure this technique would be a way to gloss up the etched graphics a little.
    However the plates have up to 220cm2 raw aluminium to be polished. If we take 100ma per cm2 that means a whopping 22A current. Is that correct? Most DC supplies I can find up to 10A but 20A and over is more an industrial scale right?
    The scale of it freaks me out
    I am only a small boutique manufacturer. Not industrial
    Any thoughts?

  6. Quick question: is the aluminum piece conductive after electropolishing? An oxide layer would form right after electropolishing, which would render the piece nonconductive. Thanks.