Plasma polymerization of HMDSO with an atmospheric pressure plasma jet for corrosion protection of aluminum and low-adhesion surfaces

Thin functional films were deposited on aluminum with an atmospheric pressure plasma jet using hexamethyldisiloxane (HMDSO) as precursor. A high dynamic deposition rate on the order of 450 nm . m . min(-1) was achieved. Composition and structure of the thin films show a strong dependence on the downstream location of the precursor injection. A 4 mm downstream shift of the precursor injection increases the carbon content in the thin film by a factor of 2.5, as indicated by XPS analysis and alters the degree of cross-linking according to the FTIR spectra. The coating with the low carbon content (17 at.-%) provides corrosion resistance for aluminum 2024 unclad exposed for 96 h to a neutral salt spray test. The coating with the high carbon content reduces the adhesion of an epoxy resin to the surface and may be used as a release coating.