Antique metal by sanding the metal's surface, coating it in hydrogen peroxide and table salt, and then cleaning the piece. Depending on the degree of antiquing desired, multiple applications of hydrogen peroxide and salt may be necessary. For smaller items, soaking overnight in regular chlorine bleach followed by another overnight soak in vinegar provides an attractive antique finish.
While commercial metal aging products are available, most are, like hydrogen peroxide and chlorine bleach, just oxidizing agents. Oxidizing agents react with the metal atoms on an item's surface, producing oxide compounds. These oxide compounds form the discolored coating known as rust, verdigris or patina depending on the type of metal in question. While oxygen in the air naturally causes this coating to form over long periods of time, chemically antiquing metal speeds up the process by using much more powerful oxidizers.
One problem with chemically antiquing metal is that it forms a very uniform oxidized finish, which does not happen naturally. Using table salt helps alleviate this problem by scuffing up the newly oxidized surface, mimicking the natural wear and tear that metal items experience. Further scratching a metal item using a wire brush or steel wool can give an even more authentic appearance. Using acid etching followed by abrasives gives a very authentic appearance, but this method is costly and dangerous.