TiCN and metallic coatings for corrosion protection of separator plates inMCFCs

Stainless steel 304 substrates were coated with different materials in orde r to find a suitable coating material for corrosion protection of separator plates in molten-carbonate fuel cells (MCFCs). Five titanium carbonitride coatings differing in composition and morphology and a titanium monoxide co ating were deposited with chemical vapour deposition techniques. Also doubl e-layer coatings of TiN/Au and TiN/Ni were prepared. The coatings were test ed on their corrosion protection of separator plates in four different envi ronments: under MCFC-cathode or anode gas, at load or at open circuit condi tions. The corrosion behaviour was characterized using cyclic voltammetry. Corrosion rates were determined with electrochemical methods and cross-sect ion analyses of corrosion layers. Titanium nitride coatings showed the best corrosion protection. The titanium carbide and titanium monoxide coating s howed respectively less and no protection. The thin gold and Ni-coatings we re unstable. Under cathode gas, the most important corrosion protection is given by keeping the cell at load, and then a titanium nitride coating migh t provide lifetime protection. Under anode gas, corrosion is most severe at load conditions. A titanium nitride coating also gives corrosion protectio n, but not enough for lifetime protection.