Current Usage

ESOH IssuesCr⁶⁺ (CrVI, hexavalent chromium) is a known carcinogen that is strongly regulated.  Chromium electroplating liberates chromic acid (Cr⁶⁺) mist that must be ducted away to meet the workplace OSHA Cr⁶⁺ PEL and scrubbed to meet the EPA Clean Air Act emission limits.

• EPA Clean Air Act rules
• OSHA Occupational Exposure to Hexavalent Chromium (Cr⁶⁺ PEL is currently 5μgm^-3)

Exposure Personnel may be exposed at the OEM level and during depot overhaul.

• OEM and depot personnel may be exposed to Cr⁶⁺ mist during chrome plating operations, and to chromic acid solution during masking, demasking.  Emission controls required.

Alternatives, Applications, StatusA number of hard coatings are used in place of hard chrome, both for OEM use and for overhaul. The primary alternative in use today for aircraft is HVOF (High Velocity Oxy-Fuel) thermal spray of tungsten carbide coatings (WC-Co and WC-CoCr). Off-road mining vehicle hydraulics and other wear components use HVOF Cr₃C₂-NiCr. HVOF is a dry coating technology that can be used both for initial production and for rebuilding worn components. All new-design aircraft landing gear and many hydraulic actuators use HVOF in place of hard chrome, and the same coatings are frequently used by DoD depots and commercial shops for aircraft component MRO. This coating is also used for many other wear-resistant and rebuild applications, such as repair of flap and slat tracks.

For internal diameters and complex parts electroless nickel is often used. Other electroplates are being developed or evaluated, particularly for internal diameters, such as pulse-plated nanophase Co-P (nCo-P) and Ni-W, and Co composite with chrome carbide or SiC.