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Fritz Friedersdorf

This informative piece discusses the impact of corrosion on DoD aircraft, highlighting the costs and non-availability associated with corrosion. It emphasizes the importance of corrosion management and sustainment through scheduled maintenance and monitoring systems. The article delves into the significance of implementing Condition-Based Maintenance (CBM) for improved corrosion control, facilitating aircraft health monitoring, fleet management, and predictive modeling. The piece also covers the correlation between corrosion rates and mass loss, as well as the use of environmental and corrosivity sensors to predict and track corrosion levels. It concludes with the necessity of standardized measurement methods for atmospheric corrosion monitoring and the integration of monitoring systems for effective corrosion prevention.

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Fritz Friedersdorf

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  1. Aircraft Corrosion Maintenance and Sustainment Luna Innovations Incorporated  friedersdorf@lunainc.com Office 1.434.220.0148 www.lunainc.com 5 October 2017 Fritz Friedersdorf

  2. Issue of Corrosion for DoD Aviation • Corrosion increases costs and reduces availability of DoD aviation systems • $2.6 billion cost of corrosion for Navy and Marine Corps aviation (LMI 2011) • 25% of maintenance costs / 25 days of corrosion-related non-availability per year • $4.5 billion cost of corrosion for Air Force aircraft and missiles (LMI 2012) • 24% of maintenance costs / 15.9 days of corrosion-related non-availability per year • Corrosion management and sustainment for DoD aircraft is schedule based • Wash cycles are set by corrosion severity zones (TO 1-1-691) • Severe (30 days) / Moderate (90 days) / Mild (180 days) • There is a desire within DoD to implement CBM for improved corrosion prevention and control

  3. Aircraft Corrosion Health Monitoring • Individual Aircraft Tracking • Measure corrosion severity • Detect upset conditions • Predict time to next inspection • Schedule preventive maintenance • Establish long term trends • Manage inspections and maintenance processes • Perform load leveling among aircraft • Examine fleet wide trends for life cycle sustainment • Validate usage assumptions • Optimize availability and life cycle costs Fleet Management

  4. Aircraft Environment and Corrosivity Measurements • Corrosion prediction requires inputs, models, and actionable outputs that can be used by maintainers • Aircraft corrosion monitoring systems quantify: • Environmental parameters (environmental severity) • Corrosion rate of surrogate materials (corrosivity) • Sensors for use in environment and corrosivity measurements have been standardized • Electrochemical sensors are compliant with ANSI/NACE Standard TM0416-2016 • Currently a new work item within ISO

  5. Corrosion Prediction • Historically, environmental severity and corrosivity are measured by average environmental conditions and/or mass loss coupons • ISO 9223 - Corrosivity of atmospheres - Classification, determination and estimation • Environmental parameters of significance • Relative humidity • Time of wetness • Amounts of corrosive contaminants • Temperature • Location based average conditions have limited utility for individual aircraft tracking and fleet management • Recent efforts have focused on continuous, dynamic measurements and models to predict corrosion rate

  6. Aircraft Monitoring Systems • Aircraft sensor nodes include environmental and corrosivity sensors • RH and air temperature sensor • Combined sensing elements with digital output • Surface temperature sensor • RTD embedded within node enclosure material • Conductance (salt contaminants) • Gold IDE • Aluminum free corrosion rate • Aluminum alloy interdigitated electrode (IDE)

  7. Monitoring System Correlation to Mass Loss • Corrosion rate sensor output is strongly correlated to mass loss coupon measurements • AA7075-T6 mass loss coupons with / A286 SS fasteners • 45-day GMW14872 accelerated test • Both sensor and mass loss coupon response exhibit power law behavior

  8. Predictive Modeling • Instantaneous corrosion rate is dependent on environmental conditions • Non-linear / Interaction effects / Hysteresis • Environmental parameters can be used to predict corrosion rate ANN

  9. Upset Conditions • Deviation of aircraft environment from predicted conditions can be an indication of operational or maintenance issues • Isolated instances where aircraft humidity is much higher than expected humidity based on local NOAA data Corrosion monitoring system data within HH-60, Patrick AFB, FL

  10. Aircraft Operation • High altitude flight cold soaks the structure, and upon landing in a high humidity climate, condensation causes high corrosion

  11. Summary • The is a significant need for improved aircraft corrosion maintenance and sustainment • Standardized measurement methods for atmospheric corrosion monitoring are available • Machine leaning techniques may be useful for corrosion prediction • Individual aircraft monitoring can be used to quantify the effect of upset conditions and operations • Successful CBM will depend on the integration of monitoring systems, predictive models, and network systems • Output must be informative to maintainers

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