Improvement of chemical resistance of apatite/titanium composite coatings deposited by RF plasma-spraying: surface modification by chemical vapor deposition

The chemical resistance of plasma-sprayed hydroxyapatite (HA) coatings on titanium substrates was successfully improved by fluoroalkylsilane (FAS), that is. 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS17) self-assembled monolayers (SAMs) formed through chemical vapor deposition. FAS17-SAMs were formed on the topmost HA layer of HA/Ti composite coatings prepared with rf input powers of 12, 17 or 27 kW. Each sample was immersed in a pH 6 buffer solution and its solubility investigated by an ion chromatography. All of the FAS17-coated samples became very hydrophobic with contact angles of more than 130 degrees. The total amount of Ca2+ ions released from the FAS17-coated HA surface decreased in comparison with the samples not coated with FAS17. In addition, the amount of Ca2+ ions released was significantly influenced by the base HA coatings. Scanning electron microscopic observation showed less damage on the FAS17-coated surfaces even after 12 weeks' immersion in the acidic solution, demonstrating that the effectively protected the underlying HA layer. (C) 2001 Elsevier Science B.V. All rights reserved.