Reece,

My company buffs fuel tanks, bumpers and hood crown assemblies for Peterbilt Truck Company. Your project is more complicated than you perhaps first realized. Mr. Richardson is absolutely correct in that sandblasting is terribly detrimental to the aluminum surface. What you'll have to do is use the finest grit polishing grit sandpaper that will remove the sand blast surface.

You'll need to go progressively finer and you'll probably need to finish out with a 400 grit finish that could be buffed to a mirror finish. This will require the use of cotton buffing wheels with tripoli compound and you could get the proper shine with a cotton buffing wheel with a dry chrome rouge.

I doubt that you'll be able to polish the sandblast surface adequately to give yourself the mirror finish you're looking for though. My advice is to take the swing arm to a professional metal finishing shop where they have the equipment and expertise to adequately polish and buff your part.

To remove pits from aluminum, I usually have to start with 80 grit paper. Sometimes I have had to use 40 grit, if it is factory cast . I work my way up to 2000 grit with the finishing grain going the same direction as my intended polish grain. I first use a roughing compound and finishing up with white diamond or white tripoli. I found that hand blocking the surface produces better results compared to rotational sanding..you then would have to polish out alot of swirl marks with the latter technique.

Painting

Q: How can I paint over carbon fiber wheels (e.g. Specialized tri spoke, disc wheels and Zipp wheels)? How hard is it to do custom paint on carbon fiber? What materials do I need? Any recommended readings or URLs ???

A: Yes, you can paint over carbon fiber. Call JB for a pro job, or do it yourself. In my experience this is how it's done:

1. Remove stickers and their adhesives (I use DX-330 or acetone).
2. Hand sand off some of the old clear coat or paint, if present. Decals under the clear coat can be sanded smooth this way. Stop sanding immediately at any spot if you touch carbon. It is incredibly easy to remove carbon by hand sanding. Watch especially near sharp edges (airfoil trailing edges on wheels, frames and forks) and parting lines on molded parts (often along the center line of frames and wheels, often along the sides of forks). Wet sanding helps keep the dust down.
3. Clean the surface mechanically and chemically as follows:

- Mechanically clean: remove stuff like paint flakes, old bits of dried substances, stickers and their adhesives, decals, flapping plies, scale, crud, etc.

- Chemically clean: remove grease and oil: fingerprints, real grease from old bike parts, oil from the old bike chain, etc.

- One last wash: rinse and scrub with acetone until white paper towels come clean.

4. Prime using Fill'n'Sand or similar. Fill'n'sand is just a high-build primer intended to hide small imperfections, which, depending on your level of perfectionism, is optional ;-). Any similarly described product should do.
5. Paint using regular paint (Imron, Deltron, PPG, spray can, etc.) as usual. Do not exceed 100 degrees F. Some pinholes may appear. I think this may be outgassing. Bake at lower temps or let the paint dry at room temp to avoid.

See https://www.westsystem.com/webpages/u.../index.htm#2.6 for West System's recommendations for preparing a newly cured epoxy surface for paint.



* Warnings:

1. Do not media blast with any media! Not sand, not plastic, not glass beads, not walnut shells, not steel or ceramic shot. Nothing! Not at even the lightest pressure or for even the shortest time. It is incredibly easy to eat away the carbon and epoxy. Before you know it your part is ruined!
2. Do not use chemical paint strippers! They will attack the epoxy resin that holds your part together. Acetone, alcohol and other solvents are okay, but they don't remove paint.
3. Do not use heat! Some epoxies undergo glass transition as low as 150 degrees F or so. Keep it under 100 to be safe. If it is too hot to touch with your bare skin, it is too hot. That means no power tools (buffing wheels, sanding discs, etc.) and no heat gun paint strippers, etc.