A typical sheet of metal that you purchase from a metal supplier is dull and flat. To give it a glossy shine like that of chrome it needs to be polished. Polishing aluminium is a time-consuming process, but can be done with great results. Make sure you have the right tools and the patience to complete all of the steps. Half-way through the polishing process, the aluminium sheet will look cloudy and worse than when you started. Stick with it, and you will have a shiny sheet of aluminium by the time you finish.
Mix trisodium phosphate (TSP) with water per manufacturer's instructions. Purchase TSP where you find the other cleaning supplies at the hardware store. Dip a sponge in the solution and wipe the aluminium sheet to remove any oils or residue. Rinse and dry thoroughly.
Attach a wool compounding pad to a rotary polisher. Apply roughly a ½ teaspoon of cutting abrasive polish to the pad. Rub the polish around with your finger to spread evenly across the pad.
Turn on the polisher and lower it slowly to the aluminium sheet. Move the polisher back and forth and up and down across the sheet. The aluminium will turn black at first. Continue polishing until the black begins to lift. Stop occasionally to wipe the head of the polisher with a screwdriver. Wipe the residue on a towel. Polish the entire sheet.
Attach the coarsest buffing pad to the rotary polisher. Every manufacturer has a different naming system. Choose your brand's coarsest buffing pad and coarsest polish. Apply a ½ teaspoon of the polish to the pad. Polish the sheet using the same methods described in Step 3.
Repeat the polishing process, using progressively less coarse buffing pads and polish. Rinse the panel to remove any remaining residue. Do this before the final buffing step.
Attach the final buffing pad. The pad will feel similar to a soft T-shirt or sweatshirt. Apply 1/4 teaspoon of the least abrasive finish polish to the pad with your finger. Lower the rotary polisher gently. Move the polisher back and forth and side to side to bring out a chrome-like shine.
Stay out of direct sunlight while polishing. If you find that the black residue is not lifting, you may be using too much polish, causing the polisher to slide around in the polish.