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How to Passivate Copper

Bjorck DiMarco

Passivation refers to the treatment of some metals with chemical baths that makes them permanently immune to corrosion. Passivation also can refer to the application of anti-corrosives. Copper is one metal that cannot truly be altered through passivation.

Copper has a natural passivation process that can be hastened.

However, through both natural and chemical means, copper can be made resistant to corrosion.

  1. Expose copper to the elements. Although it is a gradual process that varies in speed depending upon the humidity and heat in the environment, baring copper to the outdoors is the simplest way to passivate it. Within four to eight weeks, a dull blue-green patina will form on the copper. This patina is a corrosion inhibitor.

  2. Accelerate the growth of the patina with a chemical bath of ammonium sulfate, 6 pounds; copper sulfate, 3 ounces; ammonia, 1.34 fluid ounces, and water, 6.5 gallons.

  3. Apply the mixture as a spray. Allow it to dry between six applications. Wait six hours to see the patina deepen in color. Growth of the patina film will now spread faster.

  4. Tip

    Should the ingredients for the chemical bath not be available to you, adding three grams of benzotriazole to a liter of water will produce a similar effect.


    Wearing rubber gloves and safety goggles can protect hands and eyes from harsh chemicals.