Chromic Acid for Cleaning Copper

What Is Chromic Acid?

• Chromic acid is a chemical made up of the elements chromium in one part and oxygen in three parts. Pure chromic acid is a dark-red solid flake that is water soluble and reacts violently when mixed with a base. It is highly corrosive and carcinogenic; OSHA regulates the use of chromic acid in the workplace, and it is listed as a Health Hazard Substance. Because of the hazards, chromic acid must be handled properly with limited exposure.

Safety Precautions

• Never handle chromic acid without protection such as heavy-duty rubber gloves, safety goggles and protective clothing. When using pure chromic acid, wear a respirator to prevent breathing the fumes, which are highly toxic. Although chromic-acid cleaners that contain a small amount of the chemical combined with detergents and other ingredients are weaker than pure chromic acid, they still require rubber gloves and protective gear. If a chromic-acid solution comes in contact with skin, wash the area immediately. Do not use chromic-acid solutions if you are pregnant.

How to Clean With Chromic Acid

• When cleaning with chromic acid for household use, use a home chromic-acid cleaner, available at hardware stores. You will need a basin large enough to contain your copper item. Fill the basin with water and add the chromic-acid cleaner to a dilution of one part cleaner to 10 parts water, or about 12 ounces of cleaner per 1 gallon of water. Submerge the copper piece in the solution for three to five minutes, then remove and rinse it well with water.

Alternatives to Chromic Acid

• To clean oxidized copper without exposing yourself to a hazardous material, household alternatives to chromic acid are also effective. Make a paste of salt, flour and vinegar or lemon juice and baking soda. Coat the copper with the paste and allow it to sit for 30 to 60 minutes, then rinse it in cool water. Repeat if necessary. Vinegar or lemon juice-based copper cleaners work well for small items such as platters, teapots and other household items.