New Generation ChromeFree Primer Development

1
New Generation Chrome-Free Primer Development

• E. Morris1, Lt. S. Chupp2, L. Triplett3, R.
  Patel4 and J. Stoffer5
• 1Deft Coatings
• 2Materials Directorate-Air Force Research
  Laboratory
• 3Boeing-St. Louis
• 4Boeing-Mesa
• 5University of Missouri-Rolla
• May 12, 2004

2
Overview_________________________________________
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• Introduction
• UMR, Boeing, Deft, WPAFB Consortium / AFOSR
  Funded Project
• Non-Chrome Primer Development
• Classical vs Non-Classical
• Deft Salt Spray Data
• Summary Boeing-St. Louis Results
• Identification of Commercial Source
• 3000-Hour Salt Spray Commercial Pigment
• Deft Experimental Research
• Fleet Implementation Strategy
• Future Directions
• Chrome Removal ? Primer
• Chrome Removal ? Pretreatment

3
Project Overview_________________________________
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• AFOSR Funded Research at UMR
• Initiated as a Chrome-Free Conversion Coating
  Project
• Cerium Oxide Coatings for Aluminum Alloys
• Still in Research Phase
• Chrome-Free Primer Development
• Successful Project
• Implementation Ready
• Successful Transition from Academia to Industry
• Deft, UMR, WPAFB, Boeing-St. Louis Consortium
• UMR Developed and Licensed Technology
• Defts Coating Systems / Industrial Manufacturer
• WPAFB Technical Assistance
• Boeings Evaluation and Guidance

4
Non-Chrome Primer Development____________________
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• Objectives
• Develop NC Primer per MIL-P-85582/23377
• Compatible with Current Alloys and Pretreatments
• Approach
• Initially Used Classical Approach
• Inhibitor Chosen Based on Solubility
• Similar to Chromates
• (K2Cr2O7) Too Soluble ? Blisters
• (SrCrO4) Good Solubility ? Protection
• Complex to Appropriate Solubility
• Complexing Agents
• Exchange Resins

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Non-Chrome Primer Development____________________
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• Several Problems with Classical Approach
• Appropriate Solubility Difficult
• 500 Hrs. S.S.
  3000 Hrs. S.S.
• CrCC Al 7075-T6 CrCC Al
  7075-T6
• Type I, Class N MIL
  P-85582 C2

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Non-Chrome Primer Development____________________
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• Several Problems with Classical Approach
• Alloy Dependence
• 2000 Hrs. S.S.
  2000 Hrs. S.S.
• CrCC Al 2024-T3 CrCC Al
  7075-T6
• Type I, Class N
  Type I, Class N

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New Generation Primer Development
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• Current State of the Art
• Improved Inhibitor Response / Minimized Alloy
  Dependence
• 3000 Hrs. S.S.
  3000 Hrs. S.S.
• CrCC Al 2024-T3 CrCC Al
  7075-T6
• Type I, Class N Type I,
  Class N

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New Generation Primer Development
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• Current State of the Art
• Film Properties
• Adhesion (Boeing-St. Louis)
• Flexibility (Boeing-St. Louis)
• SkydrolTM Resistant (Deft)

9
Boeing-St. Louis Evaluation _____________________
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• Bare, CrCC Al 7075-T6 after 3000 Hours Salt Spray
• 44W033 44W034
  44GY32A MIL P-85582 C2

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Boeing-St. Louis Evaluation _____________________
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• Bare, CrCC Al 2024-T3 after 3000 Hours Salt Spray
• 44W033 44W034
  44GY32A MIL P-85582 C2

11
Boeing-St. Louis Evaluation _____________________
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• Bare, SAA/Cr Seal Al 7075-T6 after 3000 Hours
  Salt Spray
• 44W033 44W034
  44GY32A MIL P-85582 C2

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Boeing-St. Louis Evaluation _____________________
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• Bare, SAA/Cr Seal Al 2024-T3 after 3000 Hours
  Salt Spray
• 44W033 44W034
  44GY32A MIL P-85582 C2

13
Boeing-St. Louis Evaluation _____________________
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• Alclad 2024-T3 Filiform
• 44W033
  MIL P-85582 C2
• Pass Pass

14
Boeing-St. Louis Overview________________________
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• 3000 Hrs. S.S.
• Deft 44W033
• 3000 Hrs. S.S.
• MIL P-85582 C2

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Boeing-St. Louis Overview________________________
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• 5000 Hrs. S.S.
• Deft 44W033
• 5000 Hrs. S.S.
• MIL P-85582 C2

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Deft Non-Chrome Primer Sampling__________________
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• Facilities Currently Evaluating Deft Non-Chrome
  Primers
• Boeing Co.
• - St. Louis - Mesa - Long
  Beach
• - Seattle - Huntington Beach
• Lockheed Martin
• - Dallas/Fort Worth
• Northrop Grumman
• - El Segundo - Long Island
• U.S. Air Force
• - WPAFB - Dayton
• U.S. Navy
• - Patuxent River

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Boeing-Mesa Evaluation __________________________
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• Bare, CrCC Al 2024-T3 Tested to 3600 Hours Salt
  Spray
• 44W033 44GN098
  MIL P-85582 C2

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Boeing-Mesa Evaluation __________________________
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• Optical Corrosion Mapping Analysis

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Identification of Commercial Source
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• Previously from Specialty Supplier
• Identified Commercial Supplier
• Provided Pigment Specifications
• Toll Manufactured (Deft Only)
• Laboratory Scale Production
• 1-lb Pigment Batches
• Pigment Production Parameters
• Well-Defined / Controlled Process

20
Screening of Commercial Pigment__________________
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• Incorporation into Primers Boeing-St. Louis
  Evaluation
• Commercial Pigment Performs Well
• 1000 Hrs. S.S.
  1000 Hrs. S.S.
• 44W034 Specialty
  44W034 Commercial
• CrCC 2024-T3
  CrCC 2024-T3

21
Primer Production Strategy_______________________
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• Screening of Commercial Source Pigment Completed
• 1-lb Pigment Batch / Lab Scale Primer Batch
• 3000 Hours at Boeing-St. Louis
• Prepare Small Scale Primer Production
• 50 - 100 lbs Pigment Batch / 25 Gallon Primer
  Batches
• Multiple Independent Batches if Necessary
• May
• Review Status
• August
• Begin Initial Production
• August / September

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Implementation Strategy__________________________
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• Implementation of Chrome-Free Primer
• Air Force Evaluation
• Lt. Stephen Chupp / CTIO
• Deft Chrome-Free Solvent-Borne Primer
• As Chrome-Free System with Deft APC Topcoat
• F-15
• John Stevens
• AETC
• SMSgt Morales

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Explanation of Coloration in Scribes
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• Coatings that Allow Corrosion
• Scribe Darkens
• Due to Nucleation of Pits / Finely Divided
  Aluminum (Dark)
• Formation of Corrosion Salts
• Al/OH/Cl Corrosion Product (White)
• Image of

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Explanation of Coloration in Scribes
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• Protective Coatings that Contain Chromates
• Typically Shiny Scribe
• Reduction of Cr6 to Cr3 in the form of Cr2O3
  (Clear/Transparent)
• Formation of Mixed Al/Cr Oxide (Transparent/Tarnis
  h)
• Image of
• Scribe Region

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Explanation of Coloration in Scribes
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• Deft Non-Chrome Primers
• Scribe Darkens Only
• Inhibitor after Migrating to Scribe (Protective
  Film is Silver or Dark)
• No Formation of White Corrosion Salts
• Metal is Protected

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Explanation of Coloration in Scribes
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• Inhibitor Migration
• Morphology of Protective Film in Scribe after
  2000 Hours Salt Spray
• Image of
• Scribe Region
• At 5000X

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Fundamental Corrosion Study ______________________
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• Design of Experiments
• Purpose
• Attempt to Grow Protective Film Seen in Scribe
• Prepared Inhibitor-Containing Solution
• Slurry of Inhibitor Pigment and DI Water
• Let Stand for Three Days
• Filtered out Pigment Particles
• Added 1 wt NaCl
• Control Solution
• Prepared 1 wt NaCl Solution with DI Water
• Exposed Al 2024-T3 Panel into Each Solution
• 8-Hour Immersion

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Fundamental Corrosion Study ______________________
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• Results of 8-Hour Immersion in Presence of
  Chlorides
• Al 2024-T3
  Al 2024-T3
• No Inhibitor Deft Primer
  Inhibitor
• (Corrosion) (No Corrosion)

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Fundamental Corrosion Study ______________________
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• Coatings Formed from Immersion in Inhibitor
  Solution
• Al 2024-T3
  Al 2024-T3
• Milky Coating Dark /
  Silver Coating
• (Isolated Deposits) (Dense
  Deposit)

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Explanation of Coloration in Scribes
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• Visual Indication of Protection
• 3000 Hrs. S.S.
  Al 2024-T3
• CrCC Al 2024-T3 Dark /
  Silver Coating
• Type I, Class N

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Fundamental Corrosion Study ______________________
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• Overview of Corrosion Study
• Imitated Protective Film Formation
• Inhibitive Species is Protective
• Identified Two Distinct Inhibitor Deposits
• White / Milky
• Silver / Dark
• Future Direction
• Identify Parameters that Dictate Film Growth
• Other Types of Colors / Deposits Should be
  Possible
• Improve Coating Technologies

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Conclusions______________________________________
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• New Generation Non-Chrome Primers
• Close to Performance of Chromated Systems
• Passed 5000 Hours Salt Spray (Process of
  Repeating)
• Visual Indication of Protection
• Strong Understanding of System Chemistries
• How it Works
• Successful Transition from Academia to Industry
• UMR, Boeing, Deft, WPAFB / AFOSR Funded Project
• Field Implementation Scheduled
• Aircraft Test Platforms

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Future Directions________________________________
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• Qualify Primer to Military and Federal
  Specifications
• MIL-P-85582
• MIL-P-23377
• Qualify to Zero VOC Specification
• Qualify to Fuel Tank Specification
• AMS-C-27725A
• Qualify to High Flex Primer Specification
• TT-P-2760
• Qualify to Self-Priming Topcoat Specification
• TT-P-2756A
• Continue Development of Chrome-Free Technologies
• Optimize Current Primers
• Explore New Theories

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Future Directions _______________________________
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• 1500 Hrs. S.S. 1500 Hrs. S.S.
  2000 Hrs. S.S.
• MIL-P-23377 MIL-P-85582
  TT-P-2756
• CrCC 2024-T3 CrCC 2024-T3
  CrCC 2024-T3
• Zero VOC

35
Current State of the Art_________________________
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• Replacement of Chrome in Primer
• 3000 Hrs. S.S.
  3000 Hrs. S.S.
• Deft Chrome-Free Primer / APC Deft
  Chrome-Free Primer / APC
• CrCC 2024-T3
  CrCC 7075-T6

36
Future Directions________________________________
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• Replacement of Chrome in Conversion Coating
• 3000 Hrs. S.S.
  3000 Hrs. S.S.
• MIL-P-85582 Primer / APC
  MIL-P-85582 Primer / APC
• CrCC 2024-T3
  CC 2024-T3

37
Future Directions________________________________
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• Complete Chrome-Free System
• 1000 Hrs. S.S.
• Chrome-Free Primer
• Bottom Half
• Of Panel Stripped
• Chrome-Free Conversion
• CC Al 2024-T3
• 
  Type I, Class N