MILP85891A MILITARY SPECIFICATION

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• MIL-P-85891A MILITARY SPECIFICATION
• PLASTIC MEDIA, FOR REMOVAL OF ORGANIC COATINGS
• PERFORMANCE AND PHYSICAL TESTING

2004 AEROSPACE REMOVAL AND COATINGS FORUM MAY
11-12, 2004 CHARLOTTE, NORTH CAROLINA
RON D. GALLIHER, P.E. AERO-TECH COATINGS REMOVAL,
INC. 9682 Heimberger Rd. Baltimore, Ohio
43105 740-862-2615 galliherrd_at_Juno.com
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Introduction

• MIL-P-85891A quality assurance requires media
  testing
• First Article inspection every two years.
• Two series of tests based on production lot
  sizes.
• Media has failed to consistently meet
  specification requirements past 17 years.
• Probability of plastic media manufactured from
  scrap material meeting all requirements is low.
• Test requirements were established based on pre
  1988 material, single media source, and limited
  testing.
• Specification authors acknowledged necessity for
  revisions based on industry experience and First
  Article testing.
• Specification requirement review and modification
  still required.

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Ron D. Galliher, P.E.Aero-Tech Coatings Removal,
Inc.

• Responsible for 1980S Battelle/Warner Robins ALC
  PMB Research.
• Investigated Hill AFB PMB operation effect on
  aircraft materials.
• Developed many early PMB test procedures.
• Participated in MIL-P-85891A development.
• Created Aero-Tech in 1987 specializing in
  MIL-P-85891A testing.

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ORIGINAL MIL-P-85891ACOMMITTEE MEMBERS
Hank Vasil NAWC, Retired
Ken Clark NAWC, Retired
Randy Ivey WR-ALC, Transferred
Ron Galliher, P.E. Aero-Tech/Battelle
Omar Deel Battelle, Retired
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Military Specification MIL-P-85891AQuality
Assurance Provisions
Requires plastic media testing to assure
conformance to prescribed process safety and
economic requirements.

• First Article inspection consisting of 22 tests
  and inspection requirements.
• Quality conformance inspections performed on
  production lot sizes.
• Charge Lot (Same type and color 50,000 lb).
• Finished Lot (10,000 lb).

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MIL-P-85891 FIRST ARTICLE TESTS
First article testing limited primarily to Urea,
Melamine and Acrylic. Other media types
generally not tested.
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19 YEARS MIL-P-85891A AND PMB TESTING EXPERIENCE

• It is unlikely
• that any production plastic media
• sample will pass all MIL-P-85891A
• requirements.
• Ron Galliher, P.E.
• Aero-Tech Coatings Removal, Inc.

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MIL-P-85891A REQUIREMENTSFIRST TEN YEARS

• Based on 1980s material and limited data.
• MIL-P-85891A committee acknowledged requirements
  to be revised following First Article experience.
• Supplier First Article testing required once or
  not at all first ten years limiting data for
  specification revision.
• Less than 10 industry wide First Article tests
  performed.
• Original MIL-P-85891A Navy committee members
  retired and specification requirements not
  revised.
• Tolerance for slight deviation in specification
  requirements.

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MIL-P-85891A REQUIREMENTSRECENT FIVE YEARS

• First Article testing enforced 2 to 3 year cycle.
• Testing required for all media types and
  suppliers.
• Tolerance for any including slight specification
  deviation eliminated.
• Media suppliers expect First Article samples
  screened prior to First Article testing.
• Data base for specification revision eliminated.

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MIL-P-85891 REQUIREMENTFAILURE RISK

• High
• Consumption
• Ash Content
• Water Absorption

• Low
• Strip Rate
• Surface Residue
• Infrared Spectrogram
• Chlorine
• Specific Gravity
• pH
• Conductivity
• Iron Content

• Moderate
• Aggressiveness
• Hardness
• Heavy Particulates
• Light Particulates
• Extract Content
• Particle Size
• Anti-Static Behavior

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Plastic Media Manufactured from Scrap Material
Media suppliers are dependent on performance and
physical properties obtainable from scrap
materials.
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Consumption Rate Most Common Failure Parameter

• First Article test primarily performed on
  Acrylic, Urea and Melamine.
• Acrylic is especially observed to fail
  consumption rate requirement.
• Acrylic is of major interest since commonly used
  in aircraft de-paint applications.
• Need independent testing to establish reasonable
  limit.

B-1 Plastic Media Blast De-paint Oklahoma City
Air Logistics Center, Tinker AFB Air Force photo
by MS Meredith Zimmerman
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Strip Rate RequirementTypically Satisfied

• Media Type Specification
  Requirement
• Type I (Polyester) 0.15 ft2/min
• Type II (Urea) 0.15 ft2/min
• Type III (Melamine) 0.15 ft2/min
• Type V (Acrylic) 0.15 ft2/min

Strip rate requirement is identical for all
except one media type. Intent was to modify
requirement after additional First Article data
was obtained. Rates for Type II, III and V are
typically 2 to 3 times requirement.
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ASH CONTENT COMMON UREA FAILURE PARAMETERRandom
Tests Performed on Raw Stock
Ash content for raw stock often not in compliance
with specification requirement. If raw stock is
not in compliance media will not be in compliance.
Samples obtained from domestic and international
sources.
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Heavy Particulates Common Failure Parameter

• Original intent to limit heavy metals.
• Heavy particulates typically plastic particles
  with slightly higher density.
• Occasionally urea or melamine found in acrylic
  sample.
• Limit based on heavy particles measured in early
  depot operation.

Limit 0.020 grams base on 100 gram sample.
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Specific Gravity Comparison

• Specific gravity similar for plastics and sand.
• Particle kinetic energy and potential damage to
  substrate proportional to mass. Kinetic energy
  mass x velocity2
• Sand provides similar kinetic energy of plastic.
• Aluminum provides two to three times the kinetic
  energy of plastic.
• Steel provides five to eight times the kinetic
  energy of plastic.

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Hardness Comparison

• Hardness along with density and particle geometry
  contributors to paint removal rate,
  aggressiveness, and residual stress.
• Contaminants have greatest potential for
  substrate erosion and pitting.
• Aluminum hardness 3 times greater than plastics.
• Steel 10 to 25 times greater than plastics.
• Sand hardness 50 times greater than plastics.

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Plastic Hardness
Increase in hardness associated with increase in
aggressiveness and strip rate. Portion of
hardness range common with all four media
types. Limits established on best guess. Urea and
melamine typically twice the consumption rate of
acrylic.
Increased aggressiveness and Strip Rate
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Also Need to Improve Test Procedures

• Heavy and light particulates.
• Current test solutions do not mix.
• Recommended replacement solution exhibits
  non-uniform density and high viscosity.
• Water absorption.
• Consider reducing test humidity from 100 to 95.
• Expect measuring more than just water absorption.
• Extract content.
• Purpose not defined.
• Filtering process unreliable.
• Anti-static behavior.
• Test is subjective.
• Surface residue.
• Test is subjective.
• Past concerns result of improper post PMB
  cleaning.
• Aggressiveness.
• Present erosion measurement test may not be
  adequate.
• Residual stress test using almen strips also a
  concern.

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MIL-P-85891A Heavy Light Particulate Test
Solution

• Original solution trichlorotriflouroethane
  P-D-680. Trichlorotriflouroethane banned.
• Specification amendment 2 solution P-D-680
  perfluoroalkane solutions do not mix.
• WPAF proposed Zinc chloride ethanol create high
  viscosity and non-uniform density solutions
  especially in higher density mixture.
• Other solutions with uniform density and low
  viscosity exist.

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RECOMMENDATIONS

• Perform selective tests on randomly selected
  production media to verify MIL-P-85891A
  compliance.
• Perform complete First Article tests on
  production samples to develop data base for
  requirement adjustments.
• Allow First Article slight deviation from
  specification requirements when safety not a
  concern until revised.
• Improve designated test procedures.
• Eliminate unnecessary tests.
• Modify specification requirements as originally
  intended.

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Aero-Tech Coatings Removal, Inc.

• 9682 Heimberger Rd.
• Baltimore, Ohio 43105
• 740-862-2615
• galliherrd_at_juno.com