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Any ideas about aluminum finish shine removal?

We have some aluminum equipment covers on a roof that are too shiny and need to be dulled down. We don't want to apply a coating that will someday require another coating. Is there a chemical process or other process that can be performed to dull down the finished aluminum surface permanently?

Richard Baxter
- Salt Lake City, Utah

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If the panels not yet installed, etch them in caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] with a chelator or in 30% phosphoric Acid at about 120 °F. If the panels are already on the roof, use a hot water spray machine or a steam cleaner ⇦ this on eBay or Amazon [affil links] and spray on phosphoric acid. The concentration in the make-up box is a function of temperature at the nozzle so you will have to experiment. Be sure then to rinse well with tap water. The concentration you need followed by the water rinse should not harm the shrubbery. A 2 oz/100 gal Sodium DiChromate rinse would retard future corrosion but would be ecologically very bad and illegal. Robert H Probert Robert H Probert Technical Services Garner, North Carolina   Try anodizing- specify matte finish. Dado Macapagal - Toronto

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There is no such thing as a permanent surface finish anyway, but I understand that you don't want to worsen your maintenance schedule. You don't say (and maybe don't know) whether they are clear coated or anodized, but I'd bet anodized. You can almost surely dull them with almost anything strongly caustic (oven cleaner ⇦ this on eBay or Amazon [affil links] , etc.) but that will strip the anodization and leave them prone to unsightly corrosion. So, like it or not, I think you'd better paint them.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey