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Mirror polishing thin aluminum sheet on both sides without warping

Q. Hello all,

We're trying to find a solution to achieve the same degree of standard grade mirror polishing on both sides of some rectangular pieces of 1 mm thick aluminium sheet, whilst retaining the flatness of the sheets.
The largest piece is 1500 mm x 300 mm (5 ft x 1 ft)

These will be components for an artwork we're trying to make, so lightness of material is imperative, hence aluminium.

The samples we received from the local polishers were bent from stress relieving as they were made from one-sided mill finished mirror-polished aluminium which was then shop polished on the reverse side.

Your thoughts would be appreciated - is electropolishing an option?

Many thanks.

Asif Khan
designer - Lodon
March 28, 2011

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and Chemical Polishing
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A. Hi,

The obverse side of bright rolled sheet is usually deliberately roughened to give grip in the rolling process and is very difficult to smooth to a mirror finish - as you have found. Although chemical or electrolytic polishing would brighten and smooth the rough side I doubt if it would produce an adequate surface finish. It would also tend to diminish the mirror properties of the bright-rolled side. Of course, I am guessing your requirements.

If feasible, I would consider glueing two thinner bright-rolled pieces together or even glueing kitchen foil to an aluminium (or other material) substrate. Is that practicable? Also consider aluminized plastic.

I feel a little guilty in saying this as my moderately comfortable retired life-style is due in great part to a lifetime of developing, promoting & supporting aluminium brightening processes!

Harry Parkes
- Birmingham, UK

Q. Hi Harry, found this old post ... I'm interested in the same sheet type as the original poster. I'm in Northampton UK, so close to you! Any new advice on sourcing the above?? THANKS! Rob

Rob Murf
- northampton UK
February 13, 2024

Ed. note: Unfortunately, we can't reach Harry of late. Hopefully he just changed his e-mail and will see this so we can get back in touch.

A. You can use the same PVD technique used to metalise car headlight reflectors. They deposit a thin layer of a suitable lacquer, heat in a oven, deposit a thin layer of aluminum in a vacuum chamber and finally deposit another layer of hard lacquer/SiO2 to prevent accidental scratching. You need a big machine. It would be quite expensive. But I suppose
it is doable.

H R Prabhakara
- Bangalore Karnataka India
March 10, 2024

Q. Hello
I'm in the process of polishing my kit built airplane and my issue occurs when polishing between two ribs or any area where the skin has little support. This results in vibration which does not allow the cutting wheel to polish properly. This is very frustrating and leaves tiny marks on the aircraft skin.
When polishing the leading edges of wings or anywhere the skin is pulled tight it works perfectly. There has to be a better way to polish this loose skin. Many thanks for your assistance!

James M Madison
July 21, 2016 - Wichita Falls

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