What Is Chrome Plating?

This page last reviewed June 11, 2015


Chrome plating is the process by which an electrical charge is applied to a plating bath containing an electrolytic salt (chromium anhydride) solution. The electrical charge causes the chromium metal in the bath to fall out of solution and deposit onto various objects (usually metallic) placed into the plating bath.

Chrome plating operations are categorized based upon the thickness of the chromium metal layer applied. In decorative plating, a layer of nickel is first plated over a metal substrate. Following this step, a thin layer of chromium is deposited over the nickel layer to provide a decorative and protective finish, for example, on faucets and automotive wheels. Hard chrome plating is a process in which a thicker layer of chromium metal is deposited directly on metal substrates such as engine parts, industrial machinery, and tools to provide greater protection against corrosion and wear. Chromic acid anodizing is an electrochemical conversion process that creates a wear and corrosion resistant surface on metal objects but does not result in a metallic chromium layer.

The electrical charge during the chrome plating process causes the hexavalent chromium to be emitted from the bath as an aerosol that, once emitted from the facility, can be inhaled and entrained inside the lungs. In a similar manner hexavalent chromium mist is generated during chromic acid anodizing operations. Thus, hexavalent chromium emissions have the potential to adversely impact public health on a statewide basis, as well as at the local community level.

Many chrome plating shops are small operations that have been in business for many years and may be located in close proximity to residences or schools. Our emission data indicate that although statewide emissions of hexavalent chromium have substantially decreased, people living in neighborhoods near chrome plating shops may still be exposed to levels of chromium that may pose health concerns.

The ARB is also investigating emissions of nickel from nickel plating. Nickel plating is an integral part of the decorative chrome plating process and is applied prior to the chromium layer. The electrical charge applied to nickel plating baths may potentially result in emissions of nickel. The Board identified nickel compounds as toxic air contaminants (TACs) in 1991, concluding that nickel and nickel compounds are carcinogens for which there is no identifiable safe exposure level. For more information on the health effects related to exposure to hexavalent chromium or nickel compounds, please see US EPA's Health Effects Notebook for Hazardous Air Pollutants

Please send questions or comments to:   mhicks@arb.ca.gov

Hexavalent Chromium Activity Home Page

California Air Toxics Program

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