High temperature fuel cells of SOFC type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced light-weight planar cells for electricity supply systems in cars and other mobile systems. Such cells, in one current design, consist mainly of metallic parts, e.g. of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of Cr-species from the inter-connect or the casing into the electrolyte/cathode interface forming insulating phases and the mutual diffusion of substrate and anode material, e.g. iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite which in both cases reduces performance and system lifetime. Protecting intermediate layers, can reduce such effects considerably if they are dense, stable and of high electronic conductivity. Perovskite-type layers (e.g. doped LaCrO3) applied with high-velocity Direct Current-Vacuum Plasma Spraying (DCVPS) promise to solve reliably such problems.