Aluminum polishing trouble, what am I doing wrong?

[Mogrunner]

I have an aluminum tube I am trying to polish. It started off as a mill finish 8 foot length of 6061 AL, and my goal from square one has been to polish it to a finish that will not leave ANY black residue on hands or clothing that touches it.

I started with 220 grit, and I sanded the whole thing lengthwise, then moved up a grit to 300, and went 90 degrees to the original grain, and kept repeating this process up to 500 grit, each time making sure the last sanding marks were completely covered up.

After that I switched to polish, a creme polish made by Blue Magic called "Metal polish cream". I just spend 90 minutes with a power buffer (9" harbor freight) after an hour of hand polishing and it still does the same damn thing, even if I clean the surface with gasoline, anything that touches it with any pressure turns black.

How do I get the #*$& thing to stop doing this?

Thanks in advance for any help guys....

[FigureLLC]

did you get it polished to satisfaction? if so, and you're just trying to get it to stop oxidizing (the black is oxidation... aluminum oxidizes pretty instantly in air), try zool seal. it's a little bit of a pain in the a$$ to use, but if you've polished an 8' table, you're not shy. i've used it with great results, and it's supposed to keep the aluminum looking freshly polished for 2-3 years, and it should eliminate the blackening issue.

[baz]

the only way to stop the oxidizing is to coat the aluminium , some options are
zoopseal, chromeplating,powdertcoating,anodizing, painting .

[Mogrunner]

thanks for the tips guys... I found place in my city that can anodize up to 20 foot material... So I will have it clear anodized. Only $25, and less work for me. They are going to skip the chem etch, so it won't loose much of the shine either!