Use of Electroplated Chromium in Gun Barrels

Current and developing weapon systems have gun tubes that use electrodeposited chrome as a protective finish on their interior bore surface. This coating protects the bore surface against the harsh environment of the hot propellant gases, and the mechanical effects of the projectile thereby increasing the life of the gun tube. However, chrome is a heavy metal which is deposited onto the tube surface using aqueous electro-deposition. The chromic acid used in the deposition process is a hazardous substance because it contains hexavalent chrome. Hexavalent chromium is a major problem when it comes to environmental pollution prevention efforts and worker safety. Hexavalent chromium, in the aqueous liquid and misting forms, is a known carcinogen which is extremely expensive to dispose of because of its toxic nature. Agencies that plate with chromium spend hundreds of thousands of dollars on environmental waste removal. These agencies incur enormous costs protecting or minimizing employee exposure to aqueous or gaseous chromic acid. In response to this hazard, OSHA has recently reduced the current Permissible Exposure Limit (PEL) established for water soluble chrome VI compounds from the current 50 micrograms per cubic meter to 5 micrograms per cubic meter. Includes some briefing charts.