STP602

    Effects of Graphite/Epoxy Composite Materials on the Corrosion Behavior of Aircraft Alloys

    Published: Jan 1976


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    Abstract

    A study was made to evaluate the potential galvanic corrosion problem when graphite-epoxy composite materials are coupled to naval aircraft alloys in the naval air-sea environment. Electrochemical measurements (open circuit potential) showed a relatively large potential difference, approximately 1 V, between the composite and the aluminum alloys 7075-T6, 7075-T651, and 5052-H38. This difference provides the driving force for the corrosion of aluminum as an anode and is cause for concern. Corrosion current data (zero impedance technique) show that these aluminum alloys and cadmium-plated steel are much more reactive than Ti-6A1-4V when coupled to graphite-epoxy (15 versus 0.002 μA/cm2). This technique provides a means of ranking the corrosion problem when graphite-epoxy is coupled to various aircraft alloys.

    Flatwise tension test data indicated significant strength losses when graphite-epoxy sandwich specimens, composite facings bonded to aluminum honeycomb, are exposed to salt spray and synthetic seawater plus sulfur dioxide (SO2) spray environments. The strength loss is not entirely due to the galvanic effect.

    Data show that galvanic coupling of the composite to 7075-T651 aluminum alloy has no discernible effect on the stress corrosion cracking behavior of the alloy but does increase its general corrosion.

    Keywords:

    composite materials, graphite composites, epoxy composites, galvanic corrosion, electrochemical corrosion, environmental tests, tension tests, corrosion environments


    Author Information:

    Fischer, P
    Chemist and head, Materials Protection Branch, Aero Materials Laboratory, Air Vehicle Technology Department, Naval Air Development Center, Warminster, Pa.

    DeLuccia, JJ
    Chemist and head, Materials Protection Branch, Aero Materials Laboratory, Air Vehicle Technology Department, Naval Air Development Center, Warminster, Pa.


    Paper ID: STP27780S

    Committee/Subcommittee: D30.07

    DOI: 10.1520/STP27780S


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