Electrochemical characterization and degradation of carbon fibre reinforced polymer in quiescent near neutral chloride media

Abstract

In a quest for a better understanding of the mechanism and contribution(s) of fresh (“un-degraded”) and degraded CFRP surfaces to galvanic corrosion of coupled metals in multi-material assemblies the electrochemical behaviour of CFRP in quiescent 50 mM NaCl was studied using electrochemical techniques. Tests using ferricyanide/ferrocyanide redox couple revealed a quasi-reversible behaviour. Under cathodic polarization, CFRP is active electrochemically evidenced by the increase in pH (to pH ≥ 10). Galvanic current densities and potentials for Al-CFRP couple comprised of freshly polished CFRP sample ranged from 15–25 µA cm−2 and ≈−660 to −850 mVSCE respectively, while the corresponding parameter for Al-CFRP couple comprised of degraded CFRP were in the range 10–25 µA cm−2 and ≈−670 to −900 mVSCE. Contrary to expectations, CFRP prior exposure to degradative high pH media before galvanic coupling did not result in an increase in the intensity of galvanic corrosion of the coupled metal.