Influence Of TiN,TiCN Coating On Corrosion Resistance Of Commercially Pure Titanium

Background and ObjectivePure titanium has a good nature of anticorrosion, because it can spontaneously form a layer of TiO₂ oxidation film on its surface which can strongly bind the metal surface. On the other hand, pure titanium will be easily corroded if this oxidation film was destroyed due to the complicate environment, unstable pH, food friction, other ions influence and adherence with so many types of bacterias in mouth. In department of stomatology, if we made an artificial tooth with pure titanium, the service life will be shortened because it easily fractured and the bad wear resistant quality. So the application of pure titanium is restricted by those defects, especially when it is used as a stent. Therefore, it is a hot topic that how to augment the performance of wear resistance with the help of surface modification technology. To investigate the effects of TiN and TiCN coating on corrosion resistance of pure titanium in the simulated oral environment, we constructed TiN and TiCN coating by multi-arc physical vapor deposition and measured the microstructure, phase diffraction, hardness and yung modulus.Materials and MethodsThe dental pure titanium commonly used in making removable denture was casted with 15 specimens sized of 10mm×l0mm×1mm. The specimens were equally randomized to group A, group B and group C. In group B and group C, the specimens were coated with a thickness of 2.5μm TiN and TiCN coating on surface by multi-arc physical vapor deposition, respectively. After microscopic energy spectrum analysis, microstructure and phase diffraction were examined by FESEM. Hardness and Young modulus of the various coating were determined by nanoindentation. The polarization curves of all specimens in artificial saliva were measured by PARSTAT'2273 electrochemical station. The data were analyzed with SPSS 17.0 software package for t test, one-way ANOVA and nonparametric test.Results1. Pure titanium will present smooth surface with silver bright and metal luster after polishing. TiN, TiN coat present a color of gold and red brown respectively and a smooth surface without peeling and bubble. SEM(x10000) showed that all the samples present a uniform and coincident surface. The EDX analysis, A group contains 100% of Ti; B group contains elements Ti and N, C group contains three elements,Ti,N and C.2. Both the microhardness and elastic modulus in group B and group C were signifiantly superior to those in group A (P <0.001). Meanwhile, both the microhardness and elastic modulus in group C were significantly higher than group B (P <0.01).3. Corrosion potential (Ecorr) was group A > group B > group C (P < 0.05). However, corrosion current density (Icorr) was significantly lower in group A than in group B and in group A than in Group C (P < 0.01), while was not significantly different in group B and group C (P > 0.05).Breakdown potential (Ebreak) was significantly lower in group A than in group B, in group A than in group C and in group B than in group C (P < 0.05).Conclusions1. The pure titanium specimen coated by TiN or TiCN did not present significant changes in microstructure by FESEM. TiN coating and TiCN coating were successfully prepared by EDX analysis, suggesting the coating technology had a quality of high reliability.2. In regarding to microhardness and elastic modulus, both TiCN coating and TiN coating were superior to pure Ti, and furthermore TiCN coating is superior to TiN coating, indicating TiCN coating were the best in compactness, abrasion resistance, and corrosion resistance.3. Both TiCN coating and TiN coating improved corrosion resistance of pure titanium in artificial saliva. However, TiCN coating were superior to TiN coating in improving corrosion resistance of pure titanium.