Accession Number : ADA256072


Title :   The Effect of a Seawater Environment on the Galvanic Corrosion Behavior of Graphite/Epoxy Composites Coupled to Metals


Corporate Author : NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD


Personal Author(s) : Aylor, D M ; Murray, J N


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a256072.pdf


Report Date : Jul 1992


Pagination or Media Count : 56


Abstract : Galvanic compatibility between graphite/epoxy (Gr/epoxy) composites and metals (HY80 steel and nickel aluminum bronze (NAB)) was evaluated in 180- day seawater galvanic couple tests and laboratory electrochemical tests. Results indicate that significant galvanic corrosion of NAB and HY80 can occur when each material is coupled to a Gr/epoxy composite containing exposed graphite fibers, with the rate of the metallic corrosion increasing as the exposed graphite fiber area in the composite is increased. Galvanic corrosion can also occur between Gr/epoxy composites with no graphite fibers initially exposed to the environment and a metal as a result of moisture absorption through the epoxy outerlayer to the graphite fibers. The electrochemical impedance spectroscopy evaluation demonstrated that Gr/epoxy composites with no graphite fibers initially exposed to the environment can act as an effective cathode for oxygen reduction in seawater. It was estimated that after 200 days' seawater exposure, 15% of the planar area of this Gr/epoxy composite contained seawater-exposed graphite fibers. The potentiodynamic polarization results suggest that short-term electrochemical testing is not a reliable method for assessing long-term galvanic corrosion behavior of Gr/epoxy-metal couples but does indicate a sensitivity to graphite fiber area effects. graphite/epoxy, composites, metals, seawater, galvanic corrosion.


Descriptors :   *METALS , *ENVIRONMENTS , *BEHAVIOR , *GRAPHITE EPOXY COMPOSITES , *GALVANIC CORROSION , *COUPLINGS , *SEA WATER , TEST AND EVALUATION , CORROSION , MATERIALS , COMPATIBILITY , GRAPHITE , STEEL , OXYGEN , BRONZE , IMPEDANCE , MOISTURE , EPOXY COMPOSITES , ABSORPTION , NICKEL , LABORATORIES , ALUMINUM , CATHODES , REDUCTION , SENSITIVITY , ELECTROCHEMISTRY , RATES , SPECTROSCOPY , FIBERS , POLARIZATION


Subject Categories : Physical Chemistry
      Laminates and Composite Materials
      Properties of Metals and Alloys


Distribution Statement : APPROVED FOR PUBLIC RELEASE