N251-020 TITLE: Computational Tools for the Prediction of Galvanic and Crevice Corrosion of Advanced Materials Relevant to Sea-Based Aviation

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Computing and Software;Sustainment

OBJECTIVE: Develop computational tools that can be used for aerospace design, to minimize galvanic corrosion risk of mixed-material couples for component geometries with occluded areas exposed to atmospheric conditions relevant to sea-based aviation.

DESCRIPTION: The recent revision of MIL-STD-889D provides a starting point for comprehensive galvanic compatibility comparison of aerospace-relevant materials in immersion conditions. However, galvanic corrosion is known to be dependent on specific atmospheric factors associated with the usage environment. Due to the interactions of electrochemical processes and atmospheric conditions, the rank ordering of galvanic compatibility in immersion may not be fully representative of the degradation rates and damage distribution experienced in service. Furthermore, significant progress has been made in modeling galvanic couples openly exposed to aggressive atmospheres, but model development is needed to capture the influence of concentration polarization and mixed materials within crevices that occur at fasteners and faying surface of structural joints. Crevice corrosion at fasteners and joints presents the greatest corrosion risk for the structural integrity of airframes.

Determining a high-level approximation of relative galvanic compatibility risk under different environments on exposed surfaces and within crevices through a user-friendly computational tool for rapid analysis would enable increased accessibility and transferability of corrosion performance information between corrosion experts, aircraft designers, and engineers. If acceptable levels of galvanic compatibility are exceeded, military standards/handbooks and technical manuals/orders for corrosion prevention and mitigation strategies could be updated to aid the Cognizant Engineering Authority and computational tool user to address these issues early in the design and deployment phases.

To account for complex geometries, galvanic corrosion rate prediction across a 3D and/or 2D geometry can provide spatial resolution of relative corrosion risk, helping to inform corrosion mitigation through both design and long-term maintenance planning (inspection guidance) of aerospace structures. Corrosion prediction across a 3D and/or 2D geometry can be difficult, due to both substructure and superstructure contributions (i.e., inner and outer mold-line material combinations), creviced geometries (fastener assemblies, lap joints, etc.), and dynamic atmospheric environments. Incorporating systematic iterations of these factors to characterize their relative contribution to the galvanic corrosion risk assessment (both in magnitude and spatial distribution) through computational tools will help inform future design efforts and sustainment programs. Identifying component-level predictions of corrosion "hot spots" under specific conditions would inform specification of corrosion protection systems and determine areas of particular importance for inspection as part of an aircraft maintenance program.

PHASE I: Design and develop an approach and initial demonstration for rapidly assessing galvanic compatibility of multiple aerospace-relevant materials and three-dimensional geometries in atmospheric conditions. Develop a computational tool framework to provide a rapid and user-friendly assessment of the galvanic compatibility in atmospheric conditions, and detail methods to address atmospheric conditions relative to assumptions and inputs based on immersion testing. Describe the formal structure for all relevant metadata and assumptions used to achieve an approach suitable of naval aircraft and operating environments. Draft an approach to couple corrosion prevention and mitigation strategies with galvanic compatibility risk from existing military standards/handbooks and technical manuals/orders. Develop a computational prediction model to assess galvanic corrosion rate prediction across a 3D and/or 2D geometry, including occluded geometries, with a subset of geometries and materials, incorporating both thin-film atmospheric and crevice corrosion conditions. Demonstrate the feasibility of the model through a limited set of tests articles using galvanic couples to obtain both current responses and physical damage distribution. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Increase the assessment of material combinations, relevant geometries, and atmospheric environments in the galvanic compatibility testing for the purposes of optimization, validation, and verification. Establish the tiered computational tool framework, with modular open system architecture, and populate it with necessary property measurements, geometric models, and environment inputs to demonstrate functionality. Provide large-scale parameter-space corrosion rate prediction across a 3D and/or 2D geometry can, highlighting conditions with the most risk (highest galvanic corrosion) or most variability (change in galvanic compatibility). Clearly identify all requirements, limitations, and assumptions of the framework and computational tools. Demonstrate the capability and user-friendly accessibility through beta-testing with naval aviation stakeholders. Conduct an operational assessment for atmospheric corrosion using test articles designed to simulate structural component exposed at a marine test site. Draft methods for implementing new materials, assessing environments, and adding new geometries for use within the tiered framework. Develop the implementation plan for delivery of capabilities to the Navy and other DoD components through U.S. Government enterprise systems and assess commercialization viability for dual-use applications.

PHASE III DUAL USE APPLICATIONS: Incorporate beta-testing results from Phase II testing to address user needs. Finalize software design and make an initial software package available for purchase to the DoD.

All marine-based industries (ships, oil and natural gas platforms, and aviation) have common risks stemming from galvanic and crevice corrosion. By developing these models, engineers in these fields can develop more resilient and safer systems more quickly to accomplish the industry specific goals.

REFERENCES:

1. Williams, K. S. and Thompson, R. J. "Galvanic corrosion risk mapping." Corrosion, 75(5), 2019, pp. 474-483. https://doi.org/10.5006/3000

2. Boswell-Koller, C. N. and Rodriguez-Santiago, V. "Statistical analysis of environmental parameters: Correlations between time of wetness and corrosion severity." Corrosion, 75(5), 2019, pp. 498-504. https://doi.org/10.5006/2970

3. Nickerson, W. C.; Amiri, M. and Iyyer, N. "Building environmental history for naval aircraft." Corrosion Reviews, 2019. https://doi.org/10.1515/corrrev-2019-0022

4. "Galvanic compatibility of electrically conductive materials. (Revision D)." United States Department of Defense, 2021. https://publishers.standardstech.com/content/military-dod-mil-std-889.

5. "MIL-STD-889D, Galvanic Compatibility of Electrically Conductive Materials (July 21, 2021)."

https://standards.globalspec.com/std/14461030/mil-std-889d

KEYWORDS: Crevice Corrosion; Galvanic Corrosion; Corrosion Modeling; MIL-STD-889D; Digital Engineering; Environmental Severity

TPOC 1: Steven Kopitzke
(301) 342-1281
Email: [email protected]

TPOC 2: Alex Lilly
(240) 948-7502
Email: [email protected]

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