Hill AFB Projects for 2005 March 15

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Hill AFB Projects for 2005March 15
Ogden Air Logistics Center

• Richard H. Buchi
• OO-ALC/MADL
• DSN 775-2993
• richard.buchi_at_hill.af.mil

Innovation Excellence
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Overview

• Alodine Process / PreKote
• Powder Coating of Magnesium Gear Boxes

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Chromated Conversion CoatingsALODINE

• Alodine has been has been the standard for a
  conversion coating for over 40 years
• OEM and Test Laboratories tout the corrosion
  protection of Alodine
• However is this corrosion protection provided on
  a repainted aircraft?

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Chromated Conversion Coating (Alodine Process)

• Laboratory
• OEM
• ALCs Depot and Field

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Laboratory Prep for Conversion Coatings
Corrosion Removing Compound (dip)

• Solvent Wipe

Chromated Conversion Coating (dip)
Rinse
Dry
Rinse
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OEM Process
Parts are checked for uniform clean (a uniform
black)
Alkaline Clean (etch/dip)
Rinse
Chromate Conversion Coated
Deoxidized
Rinse
Dry
Rinse
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Controls for the Process

• Checked daily/weekly
• pH within 0.2 units
• Material concentration.
• Bath temperature maintained at 50F
• Checked monthly
• Corrosion resistance

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Prep for Paint

• Original Equipment Manufacture (OEM)
• Laboratory Test Panel

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Problems with Chromated Conversion Coatings

• Difficult if not impossible to get needed
  thickness of the conversion coating on a repaint
• Passing corrosion resistance properties of 336
  hours
• Film weight of 40 Milligrams per square foot
  (every parameter must be perfect) Therefore a
  experienced technician, clean panels, pH and
  concentration of chemicals must be within limits)
• Very brittle. After it dries, it is transformed
  into a Ceramic. Causing cracking at rivets and
  fasteners resulting in corrosion. (Boeing
  Seattle)

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Ogden's Cr Conversion Process for F-16s
Solvent Wipe
Hydro Blast (paraffin wax)
Wash
Rinse
Scuff Sand
Mask
Corrosion Removing Compound (acid etch)
Alodine
Rinse
Rinse
Dry
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ALCs Depot and Field Cr Conversion Process

• The chromated conversion coating comes in a drum
  which may be 3,6,9,12 months old before used
• NO pH adjustments
• NO testing of the product
• NO checks of any kind to verify corrosion
  resistance
• Surface must be pristine clean
• Water Brake Free Test may not be effective
• In sufficient rinsing (soap residue)
• Painters just not paying attention

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PreKote

• It cleans
• It passivates metals
• Promotes Adhesion
• It is very forgiving
• Saved time on all weapon system tested

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Environmentally

• PreKote use has
• Reduced the maintainers exposure to a highly
  soluble, proven carcinogen
• Reduced the level of PPE required
• Reduced the number of waste streams

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Leading EdgeA-10 AC 657 D. Monthan
Alodine Side
PreKote Side
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Summary for PreKote

• The Best System Process for ALC and Field use

• Safe for
• Personnel
• Environment
• Great corrosion protection when used with a
  chromated primer
• GREAT ADHESION

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Powder Coating
F-15 Gear Box
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Test Plan for Total Powder System

• Use PreKote
• The Conversion Coating characteristics of
  PreKote were first observed when it was used to
  clean magnesium camera parts.
• The PreKote stopped flash corrosion of magnesium
  and provided good adhesion for the application of
  the primer.
• Correct over temperatures and bake times

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Cross Hatch Adhesion Testing
Cr Primer Cr Primer Topcoat
Topcoat Only
Non-Cr Primer N.Cr Primer T.C. H. S.
Control
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170 Hours in Neutral Salt Fog Corrosion Chamber
Cr Primer Topcoat Non-Cr Primer Topcoat
Non-Cr Primer H.S. Cr Primer Topcoat
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500 Hours in Neutral Salt Fog Corrosion Chamber
High Solid Cr Primer Topcoat
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Next TestingBetter Cleaning

• As a result of the first testing new testes were
  conducted
• Vigorous Scrubbing with a Bristle Brush
• Ultrasonic Cleaning

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170 Hours in Neutral Salt Fog Corrosion Chamber
Powder Cr Primer
Topcoat
H.S. Cr Primer Powder Topcoat
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500 Hours in Neutral Salt Fog Corrosion Chamber
H.S. Cr Primer Powder Topcoat
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Fifth Test

• Sixty panel test
• Dow 7 conversion coating
• Best cleaning process
• Alcohol scrub
• Soap scrub
• PreKote
• Chromated primer / non-chromated
• High Solid primer / powder primer
• Best paint system
• One or two coats

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High Solids Primer and Topcoat Best Cleaning
Process
168 hours in Neutral Salt Fog
Alcohol Scrub Soap Scrub PreKote
Cr Primer Topcoat Primer Topcoat
Topcoat
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Powder Paint Chromated Primers Best Cleaning
Process

71 hours in Neutral Salt Fog
Soap
PreKote
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High Solids Paint Topcoat / Primer

96 hours
400 hours

Topcoat Primer
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High Solids Primer and TopcoatChromated /
Non-chromated
96 hours in Neutral Salt Fog
Non-Cr Cr Primer
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High Solids Paint Primer and Topcoat / Primer
400 hours
192 hours
Primer
Primer and Topcoat
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Dow 7 - High Solids Paint Topcoat / Primer
360 Hours
1900 Hours
Topcoat
Primer
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Dow 7 - High Solids Primer TopcoatChrome
Primer / Non-Chrome Primer
1900 Hours
1900 Hours
Cr Prime
Non-Cr Prime
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Dow 7 Powder Paint Non-Chrome Primer / Chrome
Primer
1600 Hours
1600 Hours
Non-Chrome Power
Chrome Powder
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Conclusions

• The factory Chromic Acid treatment (Dow process)
  on the stripped parts dies (becomes inactive)
• Dow 7 treatment greatly increased adhesion and
  corrosion resistance
• PreKote is better than soap and much better than
  alcohol
• A two coat system degrades corrosion / adhesion
  resistance
• Any inhibited coating works with Dow 7

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QUESTIONS