Make an acidic copper solution. Measure 2 oz of muriatic acid with a disposable plastic measuring cup. Pour the acid into a plastic container that can be sealed. Wrap 2 feet of 14 gauge copper wire tightly so it can fit into the container opening. Carefully submerge the copper wire in the muriatic acid. Cap the container to prevent dust and other contaminants from entering the container. Do not seal the container completely as this may increase the risk of explosion from a build up of gas pressure in the container. Allow the solution to rest for 3 to 5 days. Leave the container in a cool, well ventilated environment.
Mix 20 parts of water to 1 part of acidic copper solution. Measure the water and acid solutions with the measuring cup.
Transfer the dilute acidic solution to an all-plastic spray bottle. Spray bottles that contain metal parts will quickly corrode in the presence of the acidic solution.
Clean the metal surface by rubbing it with steel wool. A steel brush can also be used for quick cleaning of large areas.
Spray the clean metal surface with the dilute acidic solution. Ensure that the entire surface is covered with the acidic solution to encourage even rusting. The area in which you are working must remain well ventilated. Leave the sprayed metal to dry for 20 minutes.
Spray a second coat of dilute acidic solution over the metal surface. Allow the rust to develop. Significant rusting should be evident within an hour of the second coat of acid.