Remove Aluminum but Leave Copper

What thickness?

What shape?

Is it a pan?

How joined?

Give details.

Aluminum can be etched. _{(So can copper)}

Thermal shock?

Thickness - Aluminum layer is 1/4" and Copper is 1/16"..

I used a laser to cut a pattern on the copper layer.. and cutting caused some melt aluminum to redeposit of cliff of the copper. I do not want to polish the copper, nor can I polish the tight corners..

So, essentially you are looking to clean up the edges of your pattern where the aluminum melt "wicked" up the copper edge to sharpen the edge definition of your pattern?

The acid based methods will undercut the pattern into the aluminum a bit so you'll need to watch your exposure time closely.

Muriatic acid will eat the aluminum right off the copper. About $4 a gallon at most hardware stores.

Wear rubber gloves it eats skin if exposed to long. Blah blah blah some other safety stuff as well.

Muriatic acid is just a crude grade of hydrochloric acid, and as such will dissolve the copper even more aggressively than it attacks the aluminum.

Yes it is and no it won't.

Have a look at http://www2.uni-siegen.de/~pci/versuche/english/v44-24-1.html

I stand corrected. I guess I'm not too old to learn something.

What, you gonna tell it you love it and then have it fall apart when it finds out the truth??

Mercury also works well but is rather dangerous so is included only for method comparison.

I remember depositing mercury on copper as a child. Doesn't it amalgamate with the copper?

Aluminium corrodes at an alarming rate forming a protective layer that prevents further corrosion, Mercury destroys Aluminiums ability to form its protective layer.

Link

Effectively it forms a powdery oxide byproduct that should leave the copper untouched (ie- the Mercury reacts with the Aluminium but not the Copper, allowing removal)

I haven't checked melting points, but maybe the aluminum could be melted off. [?]

Simply select an acid that dissolves aluminium without dissolving copper. Get a professional chemist involved with the initial trials.

Lye or acid and close supervision with water on hand to arrest the reaction when the required result is achieved. (or to wash yourself if you mess up)

Work safe.

May I compliment you on an excellent and practical suggestion?

As a kid I put an aluminum soda can in a container filled with Drano. The Drano took off the aluminum and left behind a thin plastic film that was inside the can. The solution became very hot and caused the glass container we were doing it in to break.

Eating off the aluminum is easy and the suggestions given are all good.

However, 1/4" Aluminum, seems to me there is more value in the aluminum than there is the copper. You eat off all that aluminum and that is a lot of money wasted. Not to mention far more chemical reaction than what I had with an aluminum soda can.

I'm inclined to think that it would be more feasible melting the aluminum off, or at least most of it off, then if there is any aluminum residue to finish that off in a solution.

That way you can salvage the aluminum and sell it for scrap. Aluminum at $1.85lbs I'd say it's worth salvaging what you can.

Then again that also depends on how much material you are dealing with. It would be a good idea to run a break even analysis.

Melt it off the clean it up alunimium residue and other impurities with sodium hydroxide.

When Aluminum is bonded to Copper, a layer of four inter-metallic compounds is formed at the interface. The thickness of this layer depends on how the two metals were joined and their thermal history since joining. This (by the way) is the root cause of many electrical fires. You should not join aluminum and copper unless you have accounted for this. Anyway, you can remove the aluminum layer with potassium hydroxide, HCL and hydrogen peroxide (2:1) as well as other chemicals. But when your etching gets to the inter-metallic layer, it may stop. The rest may need to be removed mechanically (sanding or sandblasting).