Reducing

1
Reducing Hexavalent Chrome Exposure
2006 Air Force Corrosion Program Conference
March 13-17, 2006Macon, GA

• Larry Triplett
• Environmental RD
• Boeing Phantom Works
• larry.triplett_at_boeing.com
• 314-232-2882

2
Worker Protection

• Ideal Solution Eliminate all Hexavalent Chrome
  form aircraft production and maintenance
• Not practical in near term and thousands of
  existing aircraft will contain chrome until they
  are retired
• Near Term Boeing Solution - Reduce chrome
  exposure while maintaining corrosion protection
• Replace SOME hex-chrome materials with chrome
  free alternatives
• Revise processes to minimize chrome exposure
  where hex-chrome is still used

3
Boeing St. Louis Approach

• Phased implement of non-chrome replacement
  coatings and processes
• Exterior Coatings
• Lowest risk to aircraft
• Highest exposure risk to workers (application and
  removal)
• Interior tie coats
• Lower risk to aircraft parts originally coated
  with chromate primer
• Chrome free system surface treatment and primer
• Move further into interior uses as confidence is
  gained and technology improves

4
Greatest Chrome Exposure

• Chromate containing coatings
• Coating applications
• Sanding reactivation of aged primer
• Chromate surface treatments prior to paint
  (pre-paint prep)
• Anodizing and plating operations
• Boeing St. Louis chrome reduction is focused on
  primers first and surface pretreatments second

5
Hex-Cr Free Surface Treatments

• Several potential solutions
• Most work well with chromate primer but have
  significant performance reductions in chrome free
  systems
• Multiple chrome free primers tested with
• Alodine 5700
• Solgels
• Cerium conversion coating
• PreKote
• Trivalent conversion coating

6
Production Process

• Aluminum detail parts are either chromate
  conversion coated or anodized and then primed
  with chromated primer after fabrication
• After assembly, primed
  again chromated primer
• Provides initial and
  best corrosion
  protection
• Fasteners installed
  wet with sealant or
  primer

7
Interior Primer Reactivation

• Utilize chemical reactivation of aged primer to
  avoid chrome dust generated by sanding
• Implemented on all fighter programs
• Implementing on C-17 by mid 2006
• Equivalent adhesion to epoxy primers with no
  chrome dust

8
Exterior Primer Reactivation

• Greater challenge for exterior moldline chemical
  reactivation
• Multiple coatings to reactivate
• Typically more contaminated surfaces due to
  walking traffic and fluids
• Chemical reactivation of polyurethane topcoat has
  not been proven effective

9
Exterior Primer Reactivation

• Some sanding will still be required for final
  paint
• HEPA Filter Vacuum controlled sanders are
  considered Effective Engineering Control
• Benefits achieved for chrome and Silica
  collection

10
Tie-Coat Chrome Replacement
11
Primer Only Test Results3000-hours ASTM B 117
salt spray
Al
Ti
Al
Ti
Ti
Al
Al
Ti
Chrome Free
Chrome Free
Chrome Control
Chrome Control
7075-T6
2024-T3
12
Primer Test Results 3000-hours ASTM B 117 salt
spray (coatings stripped)
Chrome Control
Chrome Free
Chrome Control
Chrome Free
7075-T6
2024-T3
13
Primer Test Results3000-hours ASTM B 117 salt
spray (coatings stripped)
Chrome Control
Chrome Free
2024-T3
7075-T6
14
Primer/Topcoat Test Results 3000-hours ASTM B
117 salt spray
Al
Ti
Al
Ti
Al
Ti
Al
Ti
Chrome Free
Chrome Free
Chrome Control
Chrome Control
7075-T6
2024-T3
15
Primer/Topcoat Test Results3000-hours ASTM B 117
salt spray (coatings stripped)
Chrome Control
Chrome Free
Chrome Free
Chrome Control
2024-T3
7075-T6
16
Primer/Topcoat Test Results 3000-hours ASTM B
117 salt spray (coatings stripped)
Chrome Control
Chrome Free
2024-T3
7075-T6
17
5000-hr. neutral salt - 2024-T3 CCC
Chrome Control
Chrome Control
Chrome Free
Chrome Free
18
5000-hr. neutral salt - 7075-T6 CCC
Chrome Control
Chrome Control
Chrome Free
Chrome Free
19
5000-hr. neutral salt - 2024-T3 CCC
Chrome Control
Chrome Control
Chrome Free
Chrome Free
20
5000-hr. neutral salt - 7075-T6 CCC
Chrome Control
Chrome Control
Chrome Free
Chrome Free
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Summary

• Replace chromates based on risk
• Exterior Coatings tie-coat first followed by
  direct to metal with chromate surface treatment
• Interior tie-coats over chromate primer
• Exterior chrome free system surface treatment
  and primer
• Other interior uses as confidence is gained and
  technology improves
• Combine chrome free surface treatments, and
  chrome free coatings technology with zero VOC,
  zero HAPs on the total aircraft

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Questions?