Presented November 04, 2021- Presentation Slides
“Corrosion Monitoring Systems to Reduce Environmental Burden and Corrosion Maintenance Costs” by Capt. Brock Andrews (ESTCP Project Overview, WP-201710)
This presentation covered efforts to train a cumulative exposure algorithm to characterize the corrosion potential of an asset based on environmental exposure. The corrosion potential can be continuously monitored to assess the cumulative exposure state of the asset which in turn can be used as an input to a Condition Based Maintenance Plus (CBM+) algorithm to more efficiently define maintenance requirements for Air Force ground support equipment and aircraft. The approach uses only readily accessible data as inputs to the algorithms to decrease or eliminate the need for on-board corrosion sensors. During algorithm development, corrosion sensor data is used in conjunction with corrosion damage measured on test coupons to develop and train the exposure algorithm. The output of the exposure algorithm ultimately feed sCBM+ algorithms offering corrosion predictive prognostics, as well as expanded asset health monitoring (by tail/asset number).
Air Force Technical Orders 1-1-691 and 35-1-3 govern wash intervals for aircraft and ground support equipment, respectively. Wash intervals are based on the stationed location of an asset and the corrosivity of that specific geographic location. These technical orders do not account for mission profiles and variations in climate observed between seasons and over time. This can result in unnecessary corrosion maintenance actions (e.g., washes, inspections and preventative maintenance actions), increased costs and exposure to hazardous materials. The presentation also discussed how this project will evaluate outdoor exposure results of test coupons and corrosion sensors at ten Air Force locations varying in geographic region and environmental severity. In addition to the ground based corrosion testing, the project also employs on-board sensors on B-1, C-5, HH-60 and C-130 aircraft. Test platforms, cumulative sensor data to-date and algorithm inputs/outputs will be shared in the presentation.
“Bayesian Network Modeling Approach to Cumulative Damage Modeling of Aircraft Coatings” by Dr. Christine Sanders (SERDP Project Overview, WP19-1289)
The environmental and mechanical conditions that an aircraft is exposed to govern the overall lifetime and maintenance cycles of protective coatings. A model that can better predict maintenance based on accumulated damage will enable maintenance cycles to be performed only when necessary as opposed to using overly conservative periodic time-based maintenance intervals based on worst case scenarios. Combining neural network- and physics-based simulations has the potential to yield models that can handle uncertainty and large amounts of data, as well as predict coating wear and optimize maintenance cycles.
This presentation discussed efforts to establish these models through the analysis of extensive historical databases and the generation of new, detailed data in operationally relevant environmental conditions. By using data from real-world environments as input for a predictive model, better decisions can be made regarding maintenance cycles and man-hours required to recoat aircraft using potentially hazardous materials . Additionally, the overall approach can be used to evaluate the maintenance cycles of other coating systems using additional characterization data.
This project aimed to reduce worker exposure to hazardous materials used in paint removal and to reduce costs during programmed depot maintenance for U.S. Navy aircraft. Naval aircraft coating systems consist of multiple layers of coatings that include a pretreatment layer, a primer, and a topcoat – all of which perform several protective functions, but can contain hazardous chemicals. Degradation of the coating system during flight and on the ground occurs over time. Accurate measurement of the condition of the coating system helps eliminate unnecessary paint removal operations. This presentation focused on two principal areas of the project: 1) monitoring and modeling changes in the coating system as a result of various exposure conditions using electrochemical impedance spectroscopy (EIS) and equivalent circuit models, and 2) modeling stress fields in the coating system that arise from flight operations that contribute to crack formation. The presentation also described the EIS models that were developed to assess the state of the coating system and the role of stress in contributing to coating system breakdown and corrosion.
Capt. Brock Andrews is a lead aerospace corrosion engineer at the Air Force Corrosion Prevention and Control Office at Robins Air Force Base in Georgia. At his current assignment, Capt. Andrews manages an extensive technical project portfolio focused on technology insertion, airworthiness, and employee health and safety. Projects are primarily on coatings and surface treatments evaluations, exposure testing and mechanical, ablative, and chemical coatings stripping methods. In addition, Capt Andrews oversees changes and revisions to the office’s 4 general series technical orders. He is the principal investigator for an ESTCP project aimed at reducing maintenance burden, cost, water usage, and hazardous material runoff by decreasing the number of aircraft washes and fine-tuning wash intervals by each asset’s exposure to corrosive environments. Capt. Andrews earned his bachelor’s degree in aerospace engineering from the University of Southern California and his master’s degree in engineering management from Embry-Riddle Aeronautical University.
Dr. Christine Sanders is the lead atmospheric chemist for the Naval Research Laboratory’s (NRL) Center for Corrosion Science and Engineering. During her 10 years at NRL, she has worked to characterize the operational conditions affecting DoD assets and the impact that the environment has on the lifetime of the materials. Her work has recently focused on updating how DoD service locations are classified for corrosion severity, the impacts of combined effects testing, and mitigation of corrosion through improved understanding of clear water rinse and wash cycles. Dr. Sanders received her doctoral degree in physical chemistry from the Ohio State University.
Dr. Steve Policastro is a materials research engineer working with NRL. Dr. Policastro’s research has focused on understanding and modeling degradation in aircraft coating systems and on modeling atmospheric corrosion in aircraft materials. He has served as the principal investigator on several research grants focused on galvanic corrosion in seawater and atmospheric systems, as well as breakdowns in coating systems. He has authored more than 20 peer-reviewed research papers and book chapters in the field of corrosion. He served on active duty with the U.S. Army. Dr. Policastro earned a bachelor's degree in engineering physics from Cornell University and then received master’s and doctoral degrees in materials science from the University of Virginia.