Accession Number:

ADA256072

Title:

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

Descriptive Note:

Corporate Author:

NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD

Personal Author(s):

Report Date:

1992-07-01

Pagination or Media Count:

56.0

Abstract:

Galvanic compatibility between graphiteepoxy Grepoxy 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 Grepoxy 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 Grepoxy 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 Grepoxy 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 Grepoxy 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 Grepoxy-metal couples but does indicate a sensitivity to graphite fiber area effects. graphiteepoxy, composites, metals, seawater, galvanic corrosion.

Subject Categories:

  • Physical Chemistry
  • Laminates and Composite Materials
  • Properties of Metals and Alloys

Distribution Statement:

APPROVED FOR PUBLIC RELEASE