Metal Plating

plating

Plating is a surface-covering technique used to deposit metal on a conductive surface. Plated metals act as a corrosion inhibitor, and have increased hardness, brilliance and wearability. Commonly plated metals include gold, silver, copper, palladium, chrome, nickel and zinc.
There are generally two plating methods:

  • Electroplating: describes the process where a chemical solution which contains the ionic form of a metal is negatively charged (by a cathode) to produce a film of non-ionic metal that binds or plates itself to the positively charged (anode) surface.
  • Electroless plating: describes a plating method that involves several simultaneous reactions in an aqueous solution without electrical power. Essentially, through the use of hydrogen, sodium hypophosphites and other chemical reactions, the material is oxidized onto the surface to be plated.
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      Use of these aqueous solutions causes the metals to alter form and become inhaled, absorbed, or ingested into the human body. For example, the chrome compound of Cr(VI), or “hexavalent chrome” is released into the environment by the chromate-containing baths used in plating. Cr(VI) is a recognized human carcinogen, especially associated with cancers of the respiratory tract such as lung cancer. The effects of chrome were made famous in the movie Erin Brockovich, where Cr(VI) was found in the drinking water of Hinkley, CA.

      Use of electroless plating can also cause fumes or dust to be released into the environment. The various nickel-based fumes and dusts from plating are carcinogenic when inhaled, absorbed or ingested in humans. Similarly, the hydrocholoric acids, sulfuric acids and other solutions used in the chemical reactions of plating can lead to advanced respiratory problems.

      The plating industry has known for decades about the hazards of the various chemicals its workers are exposed to. Rather than inform the workers, the plating industry has instead secreted this knowledge from workers and customers, and fought efforts by OSHA and the federal government to put greater controls on plating emissions.