Most advice regarding rust involves how to remove it, but there are times when you may actually want to cause metal to rust faster. Whether you are a prop maker or a DIY’er, you might need to make metal rust to get the right look for your project.
Ensure that the metal you are working with will rust.
Only metals containing iron will rust, and some iron alloys will rust slowly or not at all. Stainless steel, an alloy of iron and chromium, will be very difficult to rust. Cast iron or wrought iron will rust most easily.
Measure some hydrochloric acid into a plastic bottle.
Hydrochloric acid is readily available in low concentrations at hardware stores, often labeled as muriatic acid. Handling it carefully, pour about 2 ounces (60 ml) into a sturdy plastic bottle. You should wear rubber gloves and safety glasses when doing this.
Dissolve a bit of copper in the hydrochloric acid.
Dissolving copper into the acid solution creates a wash that will speed the rusting process. The best way to dissolve copper in the acid is to wrap a short length of copper wire into a coil and submerge it in the acid for about a week.
When leaving the copper to soak, do not cap the bottle tightly. The gases produced during the chemical reaction will cause pressure to build inside the bottle. Also, make sure to clearly label the bottle and store it out of reach of children or pets.
Copper coins can be used as well. Make sure the coin’s content is largely copper; for instance, United States pennies made after 1982 are only 2.5 percent copper. However, pennies made before 1982 are 95 percent copper.
Dilute the copper and acid solution with water.
After some of the copper has dissolved into the acid, put on protective gloves and carefully remove the copper from the solution. Once you have taken it out of the solution, you can discard it. Dilute the acid with water in a ratio of roughly 1 part acid to 50 parts water. If you used 2 ounces (60 ml) of hydrochloric acid, you should mix it with about a gallon (3.8 L) of water.
Clean your steel or iron thoroughly.
The acid and copper solution will work best when the metal is very clean. There are commercially available products designed for cleaning scale or corrosion from metal, but a wash and rinse with soap and water will generally be sufficient.
Apply the acid solution.
Apply a light layer of the solution to the metal and allow it to air dry. The acid can be applied with a spray bottle or paint brush, although the acid will quickly deteriorate any metal components of the spray bottle. Wear protective gloves and safety glasses when applying the acid solution, and work in a well-ventilated area, preferably outdoors.
Allow the metal to rust.
Within an hour, you should see noticeable rusting on the metal. You do not need to wipe or rinse away the acid wash; it will dissipate naturally. If you desire a heavier layer of rust, apply another wash of the acid solution.
Select a well-ventilated area to work in.
Peroxide can be dangerous if too much is inhaled at a time. Choose a piece of metal that is either iron or tin–both will work with this method.
Transfer the peroxide to a spray bottle.
The spray bottle will make it much easier to apply to your metal. Spray your piece of metal with a sizeable amount of peroxide. Spraying more peroxide will help to speed up the rusting process.
Sprinkle salt onto the piece of metal.
You should do this while the peroxide is still wet. The rusting process will begin almost immediately and is actually easy to see. You can pour on more or less salt depending on how thick or crusty you want the rust to be.
Let the metal piece air-dry, and don’t touch it.
If you wipe off the salt while the peroxide is still wet, you will disrupt the rusting process and cause your rust to come out blotchy. Once dry, rub the salt off and admire your work.
Experiment with this method.
While you have just read about the basic way you can use peroxide and salt to cause metal to rust, the sky is really the limit when it comes to this technique. Rub the salt off and then spray the piece with peroxide again. Try different amounts of salt or dip your metal into water once it has dried. The water will give the rust a smoother texture.
Protect your work surface, if necessary.
Spread out the metal items.
Spray the items with hydrogen peroxide.
Immediately spray the items with white vinegar.
Let the items sit for the rest of the day.