Does anyone know how to get back the brushed aluminum look on a bicycle that has scratches?

Question

how or what take out the scratches?

Answer 1

Absolutely.  Here is the way that Litespeed does it on their titanium frames.  The same process will work on aluminum -- and is even easier.

Purchase Scotch-Brite pads.  I believe the maroon ones are the correct grade, but check on this.  Not the home version that are bonded to sponge, but the kind you get at the hardware store in the abrasives section. Cut them with utility scissors into 2 inch wide strips and buff your tubes radially with the strips -- like you would buff shoes with a shoeshine rag.  Works like a charm, and you'll be happy with the result.

Edit: Mirage is right.  Most "bare" aluminum frames are either anodized of clear-coated, and aluminum oxidizes much faster than titanium.  But you can either clear coat it after you have finished, or do what I did with a Cannondale that I stripped to naked aluminum several years ago -- polish it from time to time with a rag and Mother's Mag Polish.  That one was smooth, not brushed, and looked like a brand new bike every time I polished it.

As for the thumbs down nonsense, I don't know who keeps doing this, but I often get best answer, either from the asker or the voters, for answers that have 2 or 3 thumbs down.  I think it's just bad behavior by people (mostly kids) with nothing better to do and I don't let it bother me.

Answer 2

You will first need to sand the material around the scratch down to the same level as the scratch. How course a grade of sandpaper to use depends on deepness of scratch and how long you want to sand. Get a range of papers from say, 100 to 1000.  Go from course to the finer paper, the brushed look will be the result of sanding in one direction only (for instance right to left) for the final sanding.    Go with the direction and grade of sandpaper that blends the area you fixed in with the rest of the bicycle. You must practice this on another piece of alum. before doing your frame.  Also remember although your bike will be better without scratches, you are removing material, , it will be difficult to make things look really good, and any areas you work will appear brighter until an alum oxide layer forms.

A dremel with fine frizzy steel wool type attachment may also be good for the final step where you are replicating the brushing.

Answer 3

NO NO NO! Do NOT sand an aluminum frame to rebrush it. Raw finish aluminum is anodized... sanding will provide a way for moisture to creep onto the bare metal and turn it black. Yuck.

I suggest that you live with the scratches. If you ABSOLUTELY have to and will live with the black metal then use a coarse Scotchbrite pad.

EDIT: I am sure that those who gave me thumbs down know that aluminum reacts differently than titanium and that aluminum can NOT be placed outdoors without it turning ugly. I am equally sure that the same people know that if an aluminum frame isn't painted, it is anodized, and the anodizing can be removed by sanding or scotchbrite.. or even oven cleaner. Sooo, just because you don't like the answer doesn't mean it isn't correct.