Corrosion of AlN-TiN Ceramics in 3% Nacl Solution

The corrosion behavior of nitride ceramics of different compositions, particularly AlN-TiN, 3AlN-TiN, AlN-3TiN, and Ti2AlN, has been studied in seawater (3% NaCl solution). The methods of potentiodynamic polarization curves as well as X-ray diffraction and Auger spectroscopy are employed. The AlN-TiN samples show the highest corrosion resistance. When anodic polarization of the samples increases to +1.20 V (in relation to their stationary potential -0.22 V), their surface becomes the most passive one, and the samples no more pass into the solution. In case of more positive potentials, very thin protective films form on the samples, representing a two-phase coating consisting of AlOOH and Na4TiO4. Other composite ceramics are not characterized by such exceptional stability: longer regions of active dissolution are observed on the anodic polarization curves for these ceramics. For the samples of comparatively corrosion-resistant 3AlN-TiN ceramics, two-phase corrosion products, AlOOH and Al(OH)(3), are formed. The AlN-TiN ceramic composite is recommended as the most corrosion-resistant material for seawater applications.