corrdesa time dependent corrosion simulation
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1. Alan Rose, Keith Legg, Corrdesa LLC [email protected], [email protected] 2. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Many organizations assess galvanic corrosion using tables or specs such as MIL-STD-889, MIL-DTL-14072. These are all based on Galvanic Potential, but Galvanic Current is what determines the extent of corrosion 3. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 MIL-HDBK-729 MIL-STD-889B 4. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Applying Elsyca CorrosionMasterTM , using an FEA approach to solve the relevant equations results in a map of corrosion rate/current directly on the 3-D CAD model of assembly Does not matter how complex the assembly or how many materials/coatings/surface treatments there are Gives you local current density Pattern of corrosion Width and average depth of corrosion Easy change of materials, coatings, environment Explore options, what ifs Explore what happens if the coating is damaged Effects and benefits of paints and sealants Designed for use by M&P engineers, not FEA specialists 5. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Define the problem Acquire the assembly geometry Define the assembly materials/finishes Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment 6. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 NAVAIR Public Release SPR-2012-982 Define the problem Acquire the assembly geometry Define the assembly materials Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment 7. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 NAVAIR Public Release SPR-2012-982 Define the problem Acquire the assembly geometry Define the assembly materials Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment Import assembly CAD into your standard CAD package (e.g. SolidWorks). Each component is a separate subassembly. If no CAD available, we create one from drawings, photos, or make a simplified CAD. Output an STL file (all CAD packages can do this) Lug 8. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Define the problem Acquire the assembly geometry Define the assembly materials Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment Item Material/ substrate Coating Note lug UNS A92024 Anodize, unsealed Anodize undamaged bushing Cu-Be Heat treated to HRC 34-36, Cd plated, 5m thickness Model as Cd, then when consumed, the Cu-Be polarization data will automatically be used pin stainless steel UNS S31600 Cd plated, 5m thickness Model as Cd, then when consumed, the stainless steel UNS S31600 polarization data will automatically be used Note: these are not the actual materials of construction, but close choices based on what polarization curves were available 9. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Define the problem Acquire the assembly geometry Define the assembly materials Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment Polarization curves must be taken if not in database (alloys, heat treats, coatings, passivates), and assigned to surfaces of CAD model. All data should be taken IAW our Best Practices, data managed using Data Management spreadsheet 10. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Define the problem Acquire the assembly geometry Define the assembly materials Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment Choose which surfaces are wetted. Choose electrolyte thickness, conductivity (if non-standard). CorrosionMasterTM automatically remeshes, runs FEA. Import CAD model STL file. Assign the polarization curves to the surfaces of the CAD model. Al2024 anodized, lug Cd plated CuBe bushing Cd plated 316 stainless steel pin Blue areas defined as insulator for modeling purposes 11. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Define the problem Acquire the assembly geometry Define the assembly materials Define environment & electrochemistry Build the galvanic FEA model Evaluate design options/environment Corrosion CurrentCorrosion Rate Corrosion CurrentCorrosion Rate 100m film 1000m film 12. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Evolving time 100m film1000m film 13. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 14. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 15. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 For a thicker electrolyte (lower impedance), the Cd protects the anodized Al lug much longer Each component is protected individually But protection schemes interact and destroy each other This is why we have to go back and refresh the coatings every few years Possible solutions: Use computational method to optimize system protection for entire assembly Use average corrosion rate prediction to optimize inspection interval or maintenance schedule 16. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 Present methods mainly depend simply on the potential difference between the coupled materials by referring to a published galvanic table. This may highlight risk but does not quantify the corrosion rate, and often leads to poor choices. The presented computational approach accounts for important factors such as explicit geometry, potential, current, and the time evolution of the environment or consumption/degradation of protective coatings. The thickness of the electrolyte film is very important, and when tracked with time, the user can assess the impact of the sacrificial coatings being consumed and suddenly exposing other substrates which can then significantly change the character of the corrosion. Protective coatings should not be chosen individually, but designed to operate as a system if they are to provide optimum protection for the air vehicle itself. 17. [email protected] 770.328.1346; [email protected] 847.680.9420 Corrdesa LLC 2014 This work is sponsored by the Office of Naval Research (ONR), William Nickerson, under Contract N00014-12-M-0075. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research, the US Navy, or the US Government. We would also like to acknowledge the guidance and input from; Ricardo Mendoza & Filipe Mesquita of NAVAIR, North Island Leslie Bortels & Bart Van den Bossche at Elsyca