If that old tin storage shed in your backyard is getting discolored and dingy, but you don't want to replace it, you can repaint it. Tin isn't an ideal surface for getting paint to stick, but with a little preparation and the right paint, it will work. The key is to get the surface very clean and buffed of any gloss or oils. Regular dish soap and steel wool are ideal for this purpose.
Things You'll Need
Fine-grade steel wool
Four or five cans of cans of automotive-grade flat spray primer
Seven or eight cans of regular flat spray paint
Fill your bucket with warm water and a little dish soap. Put on your rubber gloves. Dip a handful of the steel wool into the water and immediately put it to the exterior wall of the shed, near the top.
Working from the top down, scrub the entire exterior surface of the shed, frequently dipping the steel wool back into the bucket to replenish it with soapy water.
Hose down the entire surface to remove all soap. Let dry in the sun at least one day. If there are door knobs or other fixtures on the shed, tape them off with your painter's tape.
Apply a thin coat of automotive-grade spray primer, in long, even motions with the design of the exterior (horizontal motions if the siding has horizontal line, or vertical motions if it has vertical lines). Hold pieces of cardboard under the roofline to prevent the paint from getting on the roof. Cover the surface completely but make sure to keep the layer thin enough so there are no drips.
Allow the primer to dry for a day. Repeat the painting process with flat finish spray paint, again using very thin layers. Let the first coat dry, then apply a second coat.
Spray paint fumes can be harmful, so make sure you're not directly breathing them in.