Ni- and Co-based alloys, widely used in prosthetic dentistry, are submitted to corrosion processes and some allergic reaction may occur.The purification of metal intraosseous implants by the modification of alloy surface is employed to avoid their noxious influence. One of these methods is deposition of TiN layers characterized by high hardness, strength, wear resistance and good biotolerance. The high passivity of coatings should ensure their good corrosion resistance.
This paper presents the results of investigations of the corrosion resistance of PVD deposited TiN layers onto typcal dental alloys. Two types of coatings-TiN and TiN+Ti2N were deposited on the Ni-Cr-Mo type alloy (Hearenium NA typically used for casts of immovable elements facing by ceramics) and on the Co-Cr-Mo type alloy ( Wironit used for movable framing casts). These coatings were examined by means of diffraction techniques and X-ray microanalysis due to determine the chemical composition and structure of the layers. The approximate thickness of layers was stated by X-ray method. Then the corrosion behaviour was examined. The number of ions from the metallic base penetrating through the coating into the corrosive solution (artifical saliva)was determined. Also, the potentiodynamic polarization technique was used to determine the corrosion resistance of coated samples. Tests were performed in a solution of 0.9% NaCl with the potential change rate of 1 mV/s in the potential range from -200 mV to 1000mV. The results of electrochemical corrosion tests of coated samples were compared with results for based alloys. The surfaces of samples before and after corrosion tests were observed by means of SEM.
The main statement is that the coatings of titanium nitrides improve the corrosion resistance.

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