Zoran Bobić¹, Lazar Kovačević¹, Miha Čekada², Peter Rodič², Atilla Csik³, Branko Škorić¹, Vladimir Terek¹, Pal Terek^1
1University of Novi Sad, Novi Sad, Serbia
²Jožef Stefan Institute, Ljubljana, Slovenia
³Institute for Nuclear Research, Debrecen, Hungary
With a goal to assess the efficiency of physical vapor deposition (PVD) coating defect sealing by atomic layer deposition (ALD) layers, we investigated the corrosion resistance of PVD TiN and TiN + ALD Ti-O (amorphous and anatase) layers in Hank’s solution. The corrosion experiments were conducted on circular areas with 2 mm radius, employing electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) measurements. To identify defect types, quantities, and their dimensions, confocal and tactile profilometry were performed before and after the corrosion tests. Results revealed that corrosion resistance of layers is influenced by the quantity of through-thickness “critical” defects. The above-coating height of these defects is approximately half of the coating thickness, and their diameter is proportional to the coating's thickness. With an increase in their quantity the corrosion resistance of a coated system decreases. Scanning electron microscopy (SEM) of the focused ion beam (FIB) milled cross-sections revealed a uniform surface coverage by both ALD layers and effective defect sealing. Therefore, application of ALD layer over the PVD coatings emerges as a highly effective strategy for enhancing their corrosion resistance. Additionally, SEM and atomic force microscopy (AFM) analysis of a hybrid layer with anatase TiO2 revealed formation of protruding nano-features on the surfaces. Such features have promising effects on the bone-cells activity and increased implant osseointegration.