Airborne Toxic Control Measure for Chromium Electroplating and Chromic Acid Anodizing Operations Fact Sheet
Chromium electroplating (chrome plating) has been a part of California’s economy for decades. Chrome plating facilities include smaller businesses located within communities as well as larger operations that plate for the aerospace industry, located in industrial areas and within communities. Unfortunately, chrome plating operations result in emissions of the highly toxic compound hexavalent chromium. The electrolytic processes associated with plating operations cause mists or droplets containing hexavalent chromium to be released from plating tanks, which are eventually emitted into outdoor air through building openings (e.g., doors, windows, and vents) and control devices. Many of these facilities are located close to schools, residential care facilities, homes where children and elderly reside, and in disadvantaged communities. Therefore, it is critical to limit emissions from chrome plating operations in order to further reduce exposure to hexavalent chromium.
Why is CARB Concerned about Hexavalent Chromium?
In 1986, the California Air Resources Board (CARB) identified hexavalent chromium as a toxic air contaminant (TAC) under California law pursuant to Assembly Bill (AB) 1807 (Tanner, Stats. 1983, Ch. 1047) and Health and Safety Code section 39657. Specifically, the Board identified hexavalent chromium because of its toxicity and potential for exposures to this highly toxic compound. It was identified as a compound that has the potential to cause cancer with no associated threshold for cancer initiation. This means there is no level of emissions below which exposure to hexavalent chromium would be considered safe.
What is Chrome Plating and Chromic Acid Anodizing?
Chrome plating is the electrical application of a coating of chrome onto a surface for decoration, corrosion protection, and durability. An electrical charge is applied to a tank containing a chrome solution. The electrical charge causes the chrome metal particles in the tank to fall out of solution and deposit onto objects placed in the plating solution.
What are the Types of Chrome Plating Operations?
There are two types of chrome plating: decorative plating and functional plating. While decorative plating has only one coating process, functional plating encompasses two types of coating processes: hard chrome plating and chromic acid anodizing. All three of these chrome plating processes generate mists containing hexavalent chromium, which are released from the plating tank and can eventually be emitted into outdoor air after passing through a control device or as fugitive emissions from windows, doors, and vents. Other sources of hexavalent chromium emissions in chrome plating facilities include emissions from any other tanks containing hexavalent chromium in the facilities and drips/spills.
Decorative Chrome Plating
Decorative plating provides a bright, shiny finish on objects for aesthetics and basic wear protection. During the process, a thin layer of chromium is deposited, usually over a layer of nickel previously placed on the base material (e.g., brass, steel, aluminum, or plastic). Example uses include car parts, musical instruments, tools, plumbing fixtures, and furniture.
Hard Chrome Plating
Hard chrome plating produces a smooth, wear-resistant surface designed to operate under extreme conditions. During the process, a thick layer of chrome is deposited directly on the base metal. Chromium electroplating requires constant control of the plating bath temperature, electrical power, plating time, and bath composition. Example uses include hydraulic cylinders, rotors, bearings, agricultural equipment, and aircraft landing gears.
Chromic Acid Anodizing
Chromic acid anodizing generates an oxidation layer on the surface of the part that provides corrosion resistance, electrical insulation, and increased bonding for subsequent materials. The electrolytic process is used to provide a thin oxide layer on aluminum. Example uses include aircraft parts and architectural structures that are subject to high stress and corrosion, aerospace components, and precision machined parts.
What Actions has CARB Taken in the Past to Protect Public Health?
In 1988, the Airborne Toxic Control Measure for Chromium Plating and Chromic Acid Anodizing Facilities, (Chrome Plating ATCM) was adopted to reduce hexavalent chromium emissions from chrome plating facilities. The Chrome Plating ATCM reduced overall emissions by requiring add-on pollution control devices such as High Efficiency Particulate Air (HEPA) filters or packed bed scrubbers, and/or by requiring the addition of fume suppressants to the plating tanks.
In 1998, the Board adopted amendments to the Chrome Plating ATCM to establish equivalency with the federal regulation for chrome plating, the 1995 Chrome Plating National Emission Standards for Hazardous Air Pollutant (NESHAP). These amendments did not change the limits already in place but established separate limits for new sources.
In 2007, to further protect the public, CARB adopted additional amendments to the Chrome Plating ATCM (the 2007 ATCM), resulting in the current statewide emission standards, which were the most stringent and health protective emission standards applicable to chrome plating operations in the nation at that time.
In July 2017, AB 617 (C. Garcia, Stats. of 2017, Ch. 136) was signed into California law to address local air pollution in environmental justice (EJ) communities. As mandated under AB 617, California’s air quality management and air pollution control districts (Districts) must develop and adopt a community emissions reduction plan (CERP) for each selected community, in consultation with CARB, community members, and other stakeholders in the affected community. Some AB 617 CERPs identified chrome plating and other metal processing operations as a concern for many communities. Through the CERP process and EJ listening sessions, CARB staff found that people living near many of these facilities are concerned about exposure to elevated concentrations of hexavalent chromium.
How Does CARB Plan to Protect Public Health?
CARB staff is proposing to amend the Chrome Plating ATCM to further reduce and eventually eliminate emissions of hexavalent chromium from chrome plating operations and to encourage the development of alternative technologies to replace hexavalent chromium. CARB will hold two public meetings to hear the Proposed Amendments. The first meeting occurred on January 27, 2023, which provided staff input from CARB’s Board on the Proposed Amendments. Staff will be addressing the Board’s inputs and presenting the updated Proposed Amendments at the May 25 or 26, 2023, CARB Board meeting. The Board will vote on the Proposed Amendments at this meeting.