An Experimental Study Of The Effects Of Wash-Rinse Intervals On Corrosion

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An Experimental Study Of The Effects Of
Wash-Rinse Intervals On Corrosion
Developing, Fielding, and Sustaining Americas
Aerospace Force
Richard Kinzie USAF CPCO W. H. Abbott BATTELLE
I n t e g r i t y - S e r v i c e - E x c e l
l e n c e
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BACKGROUND

• The USAF aircraft wash program defines wash
  cycles based on Environmental Severity
• The cycles are 30 days, 90 days, and 120 days for
  mild, moderate, and severe locations
• The severity was determined by extensive testing
  in the late 1960s and early 1970s
• The severity was measured for most USAF basing
  locations in the late 1990s and early 2000s
• Aircraft rinsing is also required in extremely
  severe locations where extreme chloride deposits
  are expected
• Flights under 3000 over salt water require
  after flight or end of the day rinses
• A 15 day rinse program may be implemented in
  special circumstances

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INTRODUCTION

• Field Observations seem inconsistent with current
  theories of
• corrosion from NaCl acting on aluminum
• Analyses of corrosion products from various
  aircraft and sources fail to show stoichiometric
  amounts of sodium vs. chloride using multiple
  analysis techniques
• C-5 Boiler Room corrosion with high potassium
• Samples of Lap Joint corrosion product from
  multiple aircraft operating in multiple
  environments
• Corrosion studies of various exposure coupons in
  several locations failed to show significant
  differences in corrosion rates with washing
• C-141 Engine Cowlings at WR-ALC
• Bare Metal coupons in multiple locations

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ENVIRONMENTAL SEVERITY MEASUREMENT

• Unique exposure racks deployed at gt150 USAF and
  multiple other DoD locations
• Corrosion rates measured and damage characterized
  on several Al alloys, steel, copper, with
  chlorides separately determined
• Comparisons made of chloride to corrosion rates
  on various materials
• Limited number of Cumulative Environmental
  Exposure Sensors (CEES), with correlation to
  exposure racks, deployed in multiple locations on
  multiple aircraft

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OBSERVATIONS

• Chemically, AgCl would not be expected to form on
  Ag coupons in the traditional outdoor environment
• There is some evidence of environmental
  chlorides in most all locations worldwide though
  this was not expected
• Atmospheric chemists have shown small amounts of
  chlorine occur from UV acting on aerosol chloride
  in the environment
• Limited testing indicates that this amount of
  chlorine at higher humidities can result in
  significantly increased corrosion rates

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Hypothesis

• If corrosion resulted via mechanism involving
  gaseous chlorine the corrodents could regenerate
  very rapidly in a high chloride, high humidity
  environment
• If gaseous chlorine was a step in the corrosion
  mechanism it is possible to explain the lack of
  stiochemetric amounts of sodium observed
• Corrosive species resulting from atmospheric
  contamination should be more rapidly deposited
  but easily removed since they should be very
  water soluble
• Corrosive species resulting from aircraft
  contaminates (oils, greases, carbon, spills)
  should be more slowly deposited but more
  difficult to remove

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Wash/Rinse Study

• Phase I
• Wash and/or rinse ground based sensors in
  different environments on different frequencies
  to determine affects on corrosion rates
• Observe affects compared to a larger body of work
  defining the affects of CPCs and other materials
  on corrosion rates on the same exposure racks and
  sensors
• Phase II
• Wash test and control C-130 aircraft in multiple
  environments on current and alternate cycles,
  measuring affects via maintenance data analysis
  and on-aircraft sensors
• Rinse test and control H-60 Helicopters on
  significantly shortened cycles in severe
  environments measuring affects via maintenance
  data analysis and on-aircraft sensors

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Effects of Wash IntervalFlorida Beach Front
Exposure
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Effects of Wash Interval¼ Mile Inland Florida
Exposure
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Effects of WashCentral Ohio Exposure
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Effects of WashCental Georgia Exposure
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Effects of Rinse Cycle

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Preliminary Phase I Results

• Phase I work currently in progress with exposures
  continuing
• Relative benefit of washing increases with
  increasing severity of the environment
• Benefits appear limited if wash interval is
  extended beyond a few days in very severe
  environments
• Rinse data to date has not shown the expected
  affects though testing is in the early stages

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Preliminary Phase I Conclusions

• Data to date partially, but not totally, supports
  original hypothesis
• If flight testing is consistent with preliminary
  exposure data
• aircraft wash cycles in severe environments
  cannot be relaxed, with a cost/benefit analysis
  and impacts to operations study required to
  determine if more frequent washing is justified
• Wash Cycles in mild environments potentially can
  be relaxed from 120 days to only being required
  prior to phase or iso inspections, or for
  cosmetics, except for spot cleaning is special
  areas defined for a specific weapons system

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Phase II Plan

• Pending Proposed OSD Project for Field Testing
  (approved for FY 06 funding)
• Test C-130 Aircraft based in a mild environment
  proposed to be washed on an extended cycle with
  controls on current 120 day cycle
• H-60 Helicopters in a severe environment proposed
  to be rinsed daily regardless of flight
• Test C-130s and H-60s in a common severe
  environment proposed to be washed/rinsed on
  alternative cycles with controls per existing
  USAF cycles
• Outdoor ground based studies will continue
  under the Phase I effort

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Conclusions

• Research and Development is needed to understand
  corrosion mechanisms such that effective
  maintenance actions for corrosion prevention and
  control can be developed
• Data from flight testing and ground based
  exposures measuring the effects of various
  corrosion mitigation procedures must be evaluated
  for the relative effects of the various actions
  to include sheltering, CPCs, Washing, Rinsing,
  etc.
• Development efforts are needed to correlate
  accelerated laboratory corrosion testing to
  actual service experience
• It is essential that corrosion technology be
  developed that will move us from the current
  find and fix to a predict and manage
  philosophy

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Recommendations

• Complete both ground based and flight tests of
  the affects of wash and rinse on corrosion
• Alter the USAF Wash/Rinse program in TO 1-1-691
  based on the results of this study
• Compare the relative impacts of washing and
  rinsing to other corrosion prevention and control
  measures for appropriate emphasis and focus

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