Influences of Surface Finishes on Properties of Biological Zinc Phosphate Conversion Coating on Titanium

摘要

Chemically formed phosphate conversion coatings (PCC) usually have goodadhesion strength due to in situ growth and have great potential forbiomedical applications. However, the fabrication of PCC on titanium (Ti)metals has seldom been studied because inherent chemical inertia and oxidelayer block the dissolving process. Previously, the authors successfullyfabricate intact PCC on pure Ti by a novel hydrothermal phosphorizationmethod, and the coating shows good adhesion. However, metallographicallypolished specimens are used only in order to eliminate the influences of surfacetopography. In this study, the feasibility of such method to be performed onsandpaper polished and acid-etched pure Ti are studied. Results show thatrough surface benefit the nucleation of PCC and refine the crystal size, whereas,a smooth surface allow sufficient growth of crystal grain resulting in a thickercoating with stronger adhesive strength. In spite of rough surface, PCCformation on acid-etched Ti is depressed due to the existence of titaniumhydride. All the coatings obviously improve corrosion resistance of Ti substrate.The cytotoxicity test suggests that the PCCs present no adverse effects on L-929 cells and has a cytotoxicity ranking of 0–1 grade. The study shows that thehydrothermal zinc phosphorization has a potential to be extensively used for Tibasedimplants with different surface finishes.