The methodology of deposition of fluoride conversion coatings is modified with the use of galvanic coupling, agitation of the electrolyte solution, and addition of K₂CO₃, which helps to provide a better understanding of the mechanism and new avenues to tailor the composition of the coating.

TiO₂ nanotube (TN) arrays produced by electrochemical anodization have been studied extensively in recent years as a new biomaterial for implants, drug delivery systems, immuno-isolation, biosensors, cell growth, bioartifical organs and tissue engineering. A bare TiO₂ nanotube implant has many weaknesses when placed in contact with biological systems and surface modification is a possible solution for this problem. The aim of this study is to develop a very simple method for surface modification of TiO₂ nanotubes to tailor new interfacial properties important in many biomedical applications. TiO₂ nanotubes were fabricated by electrochemical anodization of titanium plate using 70 wt% glycerol in deionized water with 1 wt% NH₄F as an electrolyte. The lyophilization method has been applied to impregnate gelatin stabilized gold nanoparticles into the TiO₂ nanotubes followed by vacuum drying. This approach for tailoring different surface chemistry of TiO₂ nanotubes develops a new platform for biomedical applications.

This study examined the effects of the anodization parameters (both surfactant in electrolyte and applied voltage) on the geometrical dimensions of nanotubes. The nanotube topography, diameter, length and wall thickness were affected by the addition of a surfactant to the electrolyte and applied voltage. As a consequence, TiO₂ nanotube arrays with mean tube diameters and wall thicknesses ranging from 65 to 120 nm and 20 to 28 nm, respectively, were obtained. The mean tube diameter was decreased by adding a surfactant to the electrolyte, whereas the length of the tube was increased. The nanotube diameter and length increased linearly with increasing applied potential. At 30 V, the tube to tube spacing was increased by adding a surfactant to the electrolyte. At 40 V, the tubular surface morphology collapsed completely when the electrolyte contained the surfactant but the tube length was not affected in the electrolyte without the surfactant. The TiO₂ structure was dependent on the heating conditions; an amorphous and anatase phase was observed at room temperature and 500°C, respectively. The mean roughness (R_a) of the nanotube surface fabricated in the electrolyte with the surfactant was lower than that without the surfactant.