Hexavalent Chromium (HC)
What is hexavalent chromium?
- Hexavalent chromium is a heavy metal that is often used in metal plating processes to coat, paint and protect base metals. Many aluminum surfaces are finished or protected using hexavalent chromium to prevent corrosion.
What are the current uses of hexavalent chromium?
- Hexavalent chromium is used to protect parts in a variety of marine, automobile, aircraft, and computer components.
Why is hexavalent chromium on the Emerging Contaminants Action List?
- Hexavalent chromium has many applications by both DoD and private industry, many that have no suitable alternatives for hexavalent chromium.
- DoD’s depots and industrial facilities are challenged to continue to meet stringent exposure standards. New environmental and occupational health information is emerging and regulations are likely to continue to evolve.
- The European Union’s RoHS and REACH regulations will result in restricting certain uses of hexavalent chromium which could affect military operations in European countries, foreign military sales, and its cost and availability.
- Hexavalent chromium is among the most effective treatments for imparting wear and corrosion resistance to structural components of tactical platforms and systems such as aircraft and ships, particularly those that operate in harsh conditions, at extreme performance levels, and require very high reliability (e.g., landing gear for carrier-based aircraft).
- DoD uses hexavalent chromium in:
- Hard-chromium plating of structural components of ships and planes, both in manufacturing new components or rebuilding worn and corroded components.
- Conversion coatings and primers to protect aluminum aircraft alloys; the coatings are uniquely “self-healing” so that they continue to protect even when scratched.
- Electrochemical processes (anodizing) to thicken and toughen the naturally-occurring protective elements in aluminum parts.
- A number of key DoD functions could be significantly affected by changing science, risk, and regulatory standards including acquisition, weapons development, maintenance operations, and cleanup.
How is DoD managing the risks of continued hexavalent chromium use?
- DoD strives to continuously reduce environmental, safety and health risks. DoD starts by complying with regulations, and then takes additional protective measures when it has determined risks are still unacceptable.
- DoD responds to new standards. For example, hexavalent chromium is an inhalation carcinogen at certain levels. In 2006, the Occupational Safety and Health Administration lowered the Permissible Exposure Limit (PEL) for workers by a factor of about ten and also required the implementation of improved work practices at facilities where workers may be exposed.
- DoD has invested over $70 million to find substitute materials and processes and to evaluate control technologies to further protect workers and reduce the costs of asset maintenance.
- These new processes and materials are beginning to be integrated into new weapons platforms such as ships, aircraft, and other military equipment.
- The Emerging Contaminants Directorate is assessing the changing regulatory climate and has identified potential risk management options (RMOs) for DoD program managers.
Where can I get more information?
- A SERDP / ESTCP technical workshop summary is available at: http://serdp-estcp.org
- The DoD Corrosion Exchange is a state-of-the-art e-portal service open to individuals and organizations from industry, academia, and government interested in corrosion of DoD weapon systems, equipment, and infrastructure: http://www.corrdefense.org
- The Hard Chrome Alternatives Team is a Tri-Service and bilateral team with Canada. You can reach HCAT at their web site, http://www.asetsdefense.org
- The ASETS database is an information resource for research, development, testing and evaluation of clean technologies in the surface engineering field including hexavalent chromium and other metals: http://www.asetsdefense.org/index/htm