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Chromate Primer Alternatives

Current Usage   

Chromated primers are used to provide corrosion protection to aircraft skins and airframe components.

 

Typical Applications

Specifications

  • Aircraft skins
  • Al airframes
  • Steel airframe components
  • MIL-F-7179
  • MIL-P-53022
  • MIL-PRF-23377
  • MIL-PRF-85582
  • TO 1-1-8
  • ESOH Issues

    Cr6+ (CrVI, hexavalent chromium) is a known carcinogen that is heavily regulated.

    • EPA Clean Air Act rules


    • OSHA Occupational Exposure to Hexavalent Chromium (Cr6+ PEL is currently 5μgm-3)


    • European Union laws (RoHS, WEEE, ELV)

    Exposure

    Personnel may be exposed at the OEM level and during depot overhaul, repaint, and operational level touch-up and repair.
    • OEM and depot personnel may be exposed in painting operations.  Emission controls, PPE required.


    • Maintainers are exposed in scuff sand and paint operations.  PPE required.

    Alternatives, Applications, Status
    Primary alternatives are barium chromate and non-chrome products.  Barium chromate is considered to be less toxic than other chromates used in primers and is a Class C1 in MIL-PRF specifications.  Non-chrome primers contain alternative inhibiters such as rare earth metals.  Zn-rich primers have long been used for steel infrastructure, and new Mg-rich primers are under development and evaluation for DoD use.  A number of alternatives are commercially available and some have been authorized and implemented.

    Common Alternatives

    Examples of Authorizations and Implementations

    Specifications

    Barium Chromate primers

  • MIL-PRF-85582 Class C1
  • MIL-PRF-23377 Class C1
  • Chrome-free primer approvals

    • Some USMC vehicles
    • USN aircraft skins, scuff sand, and touch-up of existing paint systems

  • MIL-PRF-23377 Class N
  • Chrome-free primer implementations

    • F-35 Lightning II Joint Strike Fighter
    • Apache helicopter upgrade, repair (Boeing Mesa)
    • Space Shuttle solid rocket booster Al components (NASA)