Aluminum satin finish

[Chuck]

Years ago when dabbling in electronics I can recall dropping aluminum switch panels into a bath of some sort to give it a nice matt finish. After rinsing the panels a coat of semi gloss laquer protected it. I can recall using a common household product to make the etching solution, but for the life of me I cannot now recall what we used.

Does anyone know what will etch aluminum and give it a nice matt finish?
It may have been lye or something similar. Muratic acid perhaps? I know we had it around the house, so it could not have been too exotic. We mixed it with water.

I recall it really bubbled when the aluminum was dropped in. Only a minute or so was needed. When pulled out it had a black coating that we rinsed away, revealing that nice satin sheen.

I am contemplating doing the same with the switch panels on the dash, thus the need to know. Obviously my expertise in chemistry is sorely lacking. If any one can suggest a solution (no pun intended) I would be grateful.

 

[Bill D]

Chuck
I found this

Chemically, there are ways of providing a "matte" look to the aluminum. A 1-3 ounce per gallon solution of caustic soda will provide an etch, giving a matte look. Also a solution of 5 mls Nitric Acid, 3 mls hydrochloric acid, and 2 mls of hydrofluoric acid in 1 liter of DI water will give an etched pattern. Both of these will result in a smut that needs to be removed by immersion in a nitric acid solution.
Another method of obtaining a matte finish is to bead blast or sandblast.

Bill

 

[Chris Martino]

Alternatively, you could spray the aluminum with Zinc Chromate Primer then cover with Matte Black paint. Both available at most automotive/hardware stores.

Probably less toxic at any rate...


Chris

 

[Jim Cowden]

I use caustic soda to remove anodizing if I need to weld, It sorts it out real quick.
Scotch bright is good for matting.
Jim

 

[David Morton]

Sand or bead will distort the piece, more so on panels.

 

[Chuck]

Thanks for the quick response.

I am not exactly sure what 'caustic soda' is. Is that another name for common household lye? Is there a trade name? I would assume one could obtain it at a decent hardware store.

 

[Chuck]

Thanks for the quick response.

I am not exactly sure what 'caustic soda' is. Is that another name for common household lye? Is there a trade name? I would assume one could obtain it at a decent hardware store.

 

[Scott Calabro]

Hey Chuck,
Just go to the local auto parts store and buy some mag wheel cleaner that says "good for uncoated wheels" on the label. You'll be all set.
Best,
S

 

[Tony Hunt]

Thanks for the quick response.

I am not exactly sure what 'caustic soda' is. Is that another name for common household lye? Is there a trade name? I would assume one could obtain it at a decent hardware store.

Chuck,
Caustic soda is sodium hydroxide - NaOH

Tony Hunt

 

[Phil]

Chuck
If you need to strip the aluminum clean there is an acid sold at welding supplies that will do the job..its used to clean before welding. Also your local NAPA store will also sell an aluminum cleaner that is commonly used to clean truck bodies etc., I think it comes in gallon containers. You can then brush the pieces with a variety of scotch brite pads. black being the coarsest and I think white is the finest....you can choose your finish. Also brush in one direction to avois a cross hatch look. I usually seal the parts with a clear acrylic or urethane depending on the exposure they will see. You can also send out for clear anodizing which looks good and is essentially a permanent finish as long as there is no abrasion involved.
Hope some of this helps.
Cheers
Phil

 

[dennism]

Take a look at Simple Green which has an aeronautical grade, don't use normal Simple Green on aluminum
Dennis