1. F-16 Production Non-Cr6+ Implementation
USAF Non-Chrome TIM
San Antonio, TX
January 18, 2018
Jerry Brown
Lockheed Martin Aeronautics
Materials and Processes Engineering

2. F-16 Production Non-Cr6+ Implementation
The F-16 Production Program has been working to eliminate hexavalent chromium for nearly 30 years
Lab tests and flight tests of first generation non-chrome primers in the 1990s
Flight test – Two non-chrome primers applied over chromated chemical conversion material on wings of four aircraft (Spraylat EWDY048, Dexter Crown Metro 10PW22-2)
Underlying anodize still present to some extent
Over six year period, finish system performed reasonably well with no major finish system failures
Typical finish repairs for in-service aircraft
Overall performance not deemed satisfactory for production implementation
Lab results of non-chrome primers not as good as legacy chrome primers
Concerns about ongoing dependability of new non-chrome primer products
Difficulty in limiting non-chrome primer to OML surfaces in production processes

3. F-16 Production Non-Cr6+ Implementation
The work continued in the 2007 time frame with testing of the next- generation non-chrome primers
Lab testing performed on Deft (44-GN-098, 02-GN-084, 02-GN-093), Hentzen (16708TEP, 17035GEP), Akzo Nobel (MgRich)
Exterior program
Adhesion, flexibility, corrosion tests per MIL-specs
Multiple finish stackups for F-16 OML
Interior program
Adhesion tests
Multiple substrates such as 6000 series Al, 7000 series Al, Al casting, Ti, CRES, cad-plated alloy steel
Fluid resistance tests
Carried out three times longer than MIL-spec requirements using water, lubricating oil, hydraulic fluid)
Galvanic tests (specimens put in neutral salt spray)
Alloy steel fasteners in primed and topcoated 2000 series Al panel, scribed across fastener heads)
Titanium panel attached to primed and scribed 2000 series Al panel (using Ti fasteners)

4. Corrosion Test Examples from Exterior Program

5. Galvanic Test Examples from Interior Program

6. Galvanic Test Examples from Interior Program

7. Galvanic Test Examples from Interior Program

8. Galvanic Test Examples from Interior Program

9. F-16 Production Non-Cr6+ Implementation
These programs resulted in qualification of three non-chrome primers to the F-16 internal QPLs for primers
44-GN-098 placed on FQML-P for MIL-PRF-85582
02-GN-084, 16708TEP placed on FQML-P for MIL-PRF-23377
02-GN-093 left off due to its lack of NAVAIR qualification to MIL-PRF-23377
44-GN-098 implemented first quarter 2016 at LM Aero in Fort Worth
For both exterior and interior base priming applications on F-16 components
Anodize (with hex chrome seal) or hex chrome chemical conversion material still required as pretreatment for aluminum substrates
Previous and ongoing testing at LM Aero for non-Cr6+ anodize seal and chemical conversion material has not achieved results adequate for implementation at LM in Fort Worth
44-GN-098 chosen because of its previous implementation on the F-35 program
Painters already experienced in its application

10. F-16 Production Non-Cr6+ Implementation
So…we have made progress!
But…we still have hexavalent chromium in the finish systems on the aircraft!
Anodize and anodize seal
LM uses thin film sulfuric acid anodize at Fort Worth, but chromic acid anodize still allowed for subcontractors
Chemical conversion material
Fuel tank coating
Fast drying touchup primer
Specialty intermediate primer
Achieving total non-Cr6+ implementation on production aircraft presents some unique challenges
These challenges may also have applicability to mod programs at depot locations and some organization- and commodity-level work required by Tech Orders

11. Material Replacement Challenges in Production
Application Challenges
F-16 has hundreds of finish codes for all of the different finish applications on both the exterior and interior areas of the aircraft
Different base substrates
Different pretreatments/surface preparation
Galvanic situations
Primer only areas (e.g. some interior bays)
Pretreatment only areas (e.g. electrical ground areas)
Specialty coatings (e.g. fuel tanks)
Specialty coatings (e.g. cockpit)
Many of these internal areas are not visually seen after aircraft assembly unless a problem arises
Engineering is hesitant to remove all hexavalent chromium in these situations
Some non-Cr6+ primers may not be as robust adhering to multiple substrates
Some non-Cr6+ primers do not hold up well unless topcoated
Pretreatment only areas are a great concern!

12. Material Replacement Challenges in Production
Production Process Challenges
Manufacturing processes involving detail parts do not always lend themselves to comprehensive material replacements
Some parts are partially finished at one time and completed at a much later time
Manufacturing process delays topcoating of some parts until next assembly
e.g. many aluminum parts are pretreated and primed, then put on a shelf until ready to use
Finish system must be able to hold up to storage and be capable of reactivation
Some production facilities are used for multiple programs
All programs must agree on the material replacement change at the same time
e.g. chem processing lines such as anodize and chemical conversion
All surfaces of specific detail parts are typically finished at the same time
Multiple finishes on detail parts would create a more expensive and complex production process
Non-Cr6+ materials used on external surfaces of fuselage skin must be suitable for use as interior coatings as well

13. Material Replacement Challenges in Production
Specification Challenges
The F-16 finish system is based upon separate material specifications for different components of the finish system
Anodize must meet internal LM specification or MIL-A-8625
Chemical conversion material must meet MIL-DTL-81706
Primers must meet MIL-PRF or MIL-PRF-85582
Fuel tank coating must meet AMS-C-27725
Materials are purchased to these specifications and put together to achieve the finish system goals
There is currently no total finish system specification that provides the necessary requirements for production finish operations
e.g. MIL-PRF is intended for exterior aircraft refinishing operations
Complexity of production finish systems cannot be addressed by a “one size fits all” finish approach
This speaks to the necessity of the finish code system to satisfy all requirements for the many substrates and applications

14. Going Forward
Production programs will continue to work individual finish systems that utilize hexavalent chromium to determine if material replacements are satisfactory
Testing (laboratory and beach)
Shop trials
Document development/changes
Implementation
Plan to stay involved in industry discussions on hexavalent chromium replacements
Chrome elimination working groups
Environmental working groups
Continual contact with supplier base
Progress will continue to be made in identifying non-Cr6+ material replacements that will satisfy the technical requirements for corrosion protection and aircraft performance