The corrosion properties of carbon nanotubes-reinforced apatite composite coating on carbon/carbon composite by a double in situ process

A double in situ process, combination of injection chemical vapour deposition and biomineralisation, was used to fabricate carbon nanotubes (CNTs)-reinforced apatite composite coatings on carbon/carbon composite. The SEM images and XPS spectra showed that CNTs were wrapped in apatite and the apatite layer became dense with prolonging the immersion time. The results of the corrosion resistance of the apatite composite coatings, which was evaluated by electrochemical techniques, showed a trend that the longer biomineralisation time contributed to the more stable coating in simulated body fluid. The dense apatite layer is not beneficial for the conduction of electrons, which leads to the low value of polarisation current and high value of polarisation impedance.