Electrochemical characteristics of a carbon fibre composite and theassociated galvanic effects with aluminium alloys

The electrochemical behaviour of a carbon fibre reinforced epoxy matrix composite in 3.5% NaCl and 3.5%NaCl + 0.5 M CuSO4electrolytes was examined by potentiodynamic polarisation, potentiostatic polarisa-tion and scanning electron microscopy. Exposed carbon fibres on two defined regions (“front” and “side”)are a focus of the investigation. The large size of the exposed carbon fibres on the side region is responsi-ble for a higher cathodic current density than the front region in the NaCl electrolyte. The deposition ofcopper on the front surface of composite confirmed that the significantly higher cathodic current resultedfrom the exposure of the fibres to the NaCl electrolyte. Galvanic coupling between the composite andindividual aluminium alloys (AA7075-T6 and AA1050) was used to measure galvanic potentials and gal-vanic current densities. The highly alloyed AA7075-T6 alloy and its high population density of cathodicsites compared to the AA1050 acted to reduce the galvanic effect when coupled to the composite frontor side regions.