Aluminium is a strong, lightweight metal used to make a wide range of household appliances, automobile wheels and many other applications. Polished aluminium wheels might look shiny, like chrome, while "brushed" aluminium appears duller. Many many aluminium appliances have a nice, shiny look to them, too. But aluminium is a soft metal, relatively speaking, and scratches are almost inevitable. In order to keep your aluminium looking its best, you'll need to repair those scratches. Fortunately, repairing scratches in aluminium is something that virtually any homeowner can accomplish with some sandpaper and a little -- only a little -- elbow grease.
Wash the area you intend to repair with dish soap and warm water. Scrub with a sponge to clean them, then dry with paper towels.
Sand the scratch and the surrounding area with 180-grit sandpaper. Sand with a circular motion, checking your work area often so you can stop sanding as soon as the scratch disappears. Remember that aluminium is a soft metal; depending on the depth of the scratch, the scratch could be removed more quickly than you expect.
Sand the area with 320-grit paper using a circular motion until the majority of abrasions made by the previous sanding have been removed. Wipe the area with a clean rag and inspect it carefully, noting all of the tiny scratches that remain.
Spray the area with water from a misting bottle and sand lightly with 600-grit paper, using a circular motion. Continue misting the area and lightly sanding until the area has a smooth sheen to it and all of the scratch marks caused by previous sanding have been removed. Wipe with clean rags so that old grit will not cause new scratches.
Apply a small amount of aluminium polish to a clean rag and rub in a circular motion if the 600-grit paper has not produced the sheen that you require. Be gentle, and wash off the polish with plenty of water and a clean soft cloth when done.
Apply a light coat of metal primer and allow it to dry thoroughly, following manufacturer's directions. Then spray or brush on an acrylic paint of your choice.
For light scratches to anodised aluminium, apply jeweller's rouge (available at jewellery stores and art centres) in a circular motion with a clean cloth, then carefully wipe it off. Two or even three applications may be required, depending on the depth of the scratch. Never use an ammonia-based product on aluminium.