Effects of electroless nickel plating on 441 stainless steel as SOFC interconnect

Metal nickel was electrolessly deposited in thickness of approximately 6, 8, and 10 μm on ferritic stainless steel 441. Oxidation behaviour of plated samples was investigated after isothermal ageing at 750 °C for 400 h in an air atmosphere. Microstructure examination showed that nickel oxide formed on the surface, (Fe, Ni)3O4 spinel layer at the subsurface, and chromite at the oxide scale/steel interface. No chromium species was readily detected on the outer surface. Area specific resistance measurement indicated 2.0, 3.3, and 6.3 mΩ cm2 for 6, 8, and 10 μm plating layers, respectively, all lower than that of the uncoated case, 28 mΩ cm2. Results suggested nickel plating of thickness 8 μm would be sufficient for effectively preventing Cr out-diffusion while maintaining a low electric resistivity.