Efficiency of diamond-like carbon films on corrosion protection of titanium alloys

Resumo

Ti6Al4 V substrates were coated by diamond-like-carbon (DLC) films of various thickness (0 to 285 nm). The DLC films were deposited by an electrical discharge using a magnetron cathode and a 99.999 w/o graphite target in an argon/hydrogen atmosphere. The DLC films were characterized by Roman spectroscopy and optical microscopy. It was found that thick films present higher size of micro crystallites and higher order degree of the graphite crystalline reticule than thin films. After the corrosion tests, the order degree of the graphite crystalline reticule of thick films did not suffer significant variation. Thicker films present better adhesion on the Ti6Al4V alloy than thinner films. Potentiodynamic polarization of uncoated and DLC coated Ti6Al4V alloy was carried out in 0.5 mol L-1 NaCl aqueous solution, pH 5.9. The corrosion potential of surfaces coated with DLC film shifts to less negative values and the polarization resistance increases as the thickness of the DLC film increases.

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