Finishing aluminum


sbarton22

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For a brushed finish a random orbital sander will leave a nice circular pattern or you can use a belt sander or something similar to sand straight lines. Sand the same as wood, just keep moving up grit size until you have the finish you want. You can keep going up to a mirror polished finish if you want. If you polish it I would spray with a lacquer to keep it from oxidizing. Clean the aluminum to get all of the oil and oxidation off. I use an aluminum cleaner called Arcair Protex Alclean.

Attached are some pictures of a bracket i build for my motorcycle. I had it powder coated so my goal was to get out the deep scratches that would show thru the powder coat, but it will give you an idea of what a ROS sander will look like. The last picture has some scratches from brushing the welds, but you get the idea.

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It is going to be a band on a wood turning. I'm starting with an aluminum pipe. I was thinking I would glue it up right before I turned it down to final size. But, after reading Dave's post, I might finish the wood and finish the aluminum separately and glue.

I want an aluminum look. No patina.

I didn't even realize that aluminum oxidizes.

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I didn't even realize that aluminum oxidizes.

the aluminum will start to dull quickly on a polished piece that is not coated, over time, depending on environment and what it comes in contact with, it will get white crusty layer on it. Other useful tips - Carbon steel and aluminum are dissimilar metals which means they will eat away at each other. Always use stainless steel fasteners. Concrete and aluminum don't like each other either, always coat the aluminum if it is in direct contact with concrete.

You can sand it while it is on the lathe to get keep the sanding lines in line with the ring. Be careful about moving the sand paper back and forth you will see the lines track up and down the ring (diagonal lines)

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I didn't even realize that aluminum oxidizes.

Aluminum oxides even more readily than iron. The difference is that iron oxide is water soluble, meaning that the surface of a chunk of iron will oxidize and the resulting oxide washes away, exposing fresh iron to oxidize and wash away until eventually the whole chunk rusts away. When aluminum oxidizes, OTOH, the oxide forms a skin that protects the metal underneath.

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