CTMA Project #: 170604
Problem:
- When aluminum is given the standard treatment for corrosion resistance (chromium conversion coating), active hexavalent chromium remains on the surface of the metal.
- New regulations in the European Union may restrict the operation of aircraft treated with hexavalent chromium in all of its member states.
- No good commercially available alternative exists for conversion coating of the high copper content aluminum alloys currently in use for structural aerospace applications.
Benefit:
- Process alternatives are now available when the European Union acts to restrict the use of hexavalent chromium.
- Similar regulatory restrictions may eventually be developed in the U.S.
Solution/Approach:
- Seventeen hexavalent chromium-free alternatives from seven different suppliers were tested on six aluminum alloys.
- Test samples were subjected to standard testing for salt-fog corrosion resistance, conductivity, and paint adhesion.
- Two alternative coatings were found to give promising results on the most demanding application (a high-strength aerospace alloy).
DOD Participation:
- U.S. Army (Corpus Christi Army Depot)
Industry Participation:
- CAI Resources
- Integrated Technologies
- NCMS
