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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Polishing aluminum rims for a dull matte finish
Q. Hi All,
I'm getting a blank set of spun aluminum rims. They look very smooth and shiny now and I prefer the dull matte look. As an amateur and not wanting to spend too much, how can I create that finish. The 2 things I've thought about were scotchbrite or sending to a machine shop for beadblast.
After I finish this do I need to anodize or clearcoat to protect the aluminum?
Thanks,
Off-Road vehicle hobby - Chandler, Arizona, US
2006
A. Curtis, anodizers can easily produce a matte finish by caustic (usual) or fluoride etching. The trick is stopping at the desired degree of etching Ž best to have matte samples for matching. The parts are then desmutted, anodized, dyed if desired and sealed. If you act sufficiently knowledgeable, the etching will be included in the anodizing job cost.
Etching, clear chem film and clearcoating should also work. Or, clearcoat over the anodizing described above for maximum protection. Use a coater experienced with sealed anodize substrates.
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2006
Sanding aluminum to matte finish
Q. I've had a number of bent aluminum parts fabricated and want to bring them to a relatively uniform (non-directional) matte finish.
The parts are made out of 1/4" aluminum plate. They feature approximately 15" x 15" flat faces with 0.75" radius bends. The pieces are mill finish, but have light some scuffing from the deburring machine.
I've mirror polished aluminum before by sanding 300-1200 using a dual action sander and then compounding with nuvite and a rotary buffer. I've always noticed strong patterning from the sander path before compounding (like the pattern in freshly mown lawn) which I want to avoid on these pieces, but apart from that larger scale patterning I'd be happy with the surface finish at around 600. Are there any tips for avoiding these patterns? Is there a way of handling the sander to avoid this patterning, or would using a random orbital sander help?
Additionally, since the parts feature bends and there are relatively few pieces, I am wondering if I would be better off finishing them by hand, but I am unsure whether it would be possible to achieve a decent non-directional finish this way.
Any tips on technique/process would be greatly appreciated!
Designer - New York, New York, USA
September 6, 2019
A. Hi Robert,
Is sandblasting with aluminum oxide an option for you? This is a very common method of achieving the finish you describe. Like sanding, it's a bit of an art, but the results are very nice.
Rachel Mackintosh
lab rat - Greenfield, Vermont
September 7, 2019
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Thanks for your response Rachel! Blasting does seem like a good option. I'm also curious whether etching could work. - New York, New York, USA September 8, 2019 Robert - Green Mountain Falls, Colorado September 9, 2019 |
A. Hi Robert,
There is sort of etching I know as 'Satin Mask' (though I'm not sure what others would call it) that involves immersion in a tank of phosphoric acid with ammonium bifluoride and stabilizers. It evens out surface deformities such as milling marks and results in a satiny, near-matte finish that takes anodizing beautifully. Definitely ask your anodizer if they offer this as a surface preparation! It is much less labor intensive than hand-blasting to uniformity.
Rachel Mackintosh
lab rat - Greenfield, Vermont
September 9, 2019
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