Abstract: An electrical interconnect device for a planar fuel cell, comprising solid oxide electrolyte (44), an anode and a cathode (42), is described. The interconnect device comprises a plate-like chromium-containing substrate (22) having gas-flow channels (28) on the cathode-side and a coating on the cathode-side. The coating comprises an oxide surface layer comprising at least one metal M selected from Mn, Fe, Co and Ni, and an M, Cr spinel layer intermediate the substrate and the oxide surface layer. The intermediate spinel layer is formed by reaction of M oxide with surface chromium oxide on the substrate. The coating material may be applied as oxide or as salt or metal, or a mixture, and then converted to oxide. The M-metal(s) may be mixed with non-M metal or be doped. Methods of application are described in which the oxide surface layer is partially reacted to form the intermediate spinel layer.