Morphological variations on titanium by AC anodizing
M.V. Diamanti, M. Ormellese, MP. Pedeferri
Politecnico di Milano, IT
Keywords: anodizing, alternating current, pitting, titanium
Abstract:Besides the widely investigated photoinduced properties of its oxides, a primary branch of application of anodized titanium is the production of biomedical implants, where a controlled roughness can lead to improvements in cell adhesion and osteo-integration of the prostheses: the possibility to tune titanium morphology is therefore essential to functionalize titanium surfaces. A new anodizing treatment was adopted: a first anodizing step in alternating current, performed in diluted HCl, aimed at modifying titanium roughness and preparing the surface for the second treatment, in direct current, aimed at producing a photoactive oxide. The latter step requires the achievement of Anodic Spark Deposition conditions (high current densities and potential differences), while the first step is straightforward, lasts few minutes and allows good tuning of surface morphology by modulating anodizing parameters. The pitting mechanism promoted by chlorides and AC on titanium generates a double texture of holes: larger craters (tenths of μm wide) with sub-micrometric holes inside. The DC anodizing treatment itself confers to the surface a nanometric porosity, which combines with the AC-produced roughness. Oxides were investigated by optical microscopy, SEM, profilometry, weight loss measurements to check pitting effects, and XRD to identify the crystallization of the oxide in DC anodizing treatment.