How to Polish Aluminium to a Mirror Finish

Bare aluminium turns dull and chalky grey as it oxidises. Polish it properly and it becomes one of the most striking finishes there is, which is why motorbike and classic car restorers love it. Here is how to go from dull to mirror with a drill.

Check for coatings first

A lot of aluminium isn’t bare. Alloy wheels are usually painted or clear-coated, many engine covers are lacquered, and some parts are anodised. Polishing compounds won’t cut through lacquer or paint, and polishing will remove anodising. If there is a coating, strip it with a suitable remover before you start.

What you need

• A drill-mounted aluminium polishing kit: coarse, medium and soft mops, a mandrel, and brown cutting and blue polishing compound
• For big flat parts, an angle grinder aluminium polishing kit saves time
• Plenty of clean cotton cloths
• Gloves, eye protection and a dust mask

Step by step

1. Clean and degrease the part thoroughly.
2. Remove deep marks first. Pitting and deep scratches need wet-and-dry paper or an abrasive before polishing. Work up to around P800 so the mops have a smooth surface to work on.
3. Cut. Load the coarse sisal mop with brown compound and work over the surface at a steady speed, keeping it moving. This removes oxidation and fine scratches.
4. Refine. Change to the white stitched mop and repeat to smooth the finish further.
5. Polish. Use the soft mop with blue polishing compound. The reflection sharpens as you go.
6. Wipe clean. Aluminium leaves black residue. Wipe with a clean cloth between stages and at the end.

Keeping the shine

Polished aluminium starts to dull again as it oxidises. A metal wax or sealant slows this down. A quick re-polish with the soft mop brings it back.

See also: motorbike and classic car brightwork.

Questions

Why is my cloth going black when I polish aluminium?

That is aluminium oxide and compound coming off, and it is normal. Keep wiping until the cloth comes away clean.

Can I polish anodised aluminium?

Polishing removes anodising. Only do it if you want the part back to bare metal.

Drill or angle grinder?

A drill for small parts and detail. An angle grinder kit for large flat panels.