Metal finishing Q&As since 1989

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Aluminum final polish before permalac

I am building a 9/11 memorial that will be placed outside. The towers are 8" X 8" X 52" and are made from extruded 6061. I have mirror polished by first sanding out the extrusion marks to 600 grit then buffing with compound. First black then brown and finishing with white. I used a sewn cotton wheel for each compound. I was cautious while polishing only to use a small amount of compound, rake my wheel often and use a separate wheel for each compound. I am pleased with the polished I have obtained but I still have swirl marks. I have tried wetting then using talcum powder but that still left swirl marks visible in sunlight. I also tried polishing by hand using a variety of metal polishes (Mothers, etc.) The hand polish leaves the aluminum milky looking. I cleaned the metal with brake cleaner before the hand polish but I'm still left with a milky look in sections. I'm wondering if I need to use maybe a wool or cotton bonnet for this final stage before I clear coat with Permalac [adv: Permalac on eBay]? Should I also use a metal polish in conjunction with the bonnet? I would like to eliminate the swirl marks because I'm afraid they will be visible under the clear coat. Also if anyone has any tips on Permalac application (i.e. baking etc.) that would be helpful. Thanks!!

Tim Swanson
Welder - San Diego California
August 31, 2011

Try a large dual action orbital polisher like a lot of auto polishers use.

James Watts
- Navarre, Florida
First of two simultaneous responses -- September 2, 2011

Only carefully pretreated aluminum can be clearcoated or painted. Chromating ,or some of new "green" pretreatments or phosphating are possible options.Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
Second of two simultaneous responses -- September 5, 2011