Thin metallic Mn50Co50 coatings (0.3 and 1 mu m) were deposited by magnetron cosputtering on bare and on 100 h preoxidized ZMG232L stainless steel substrates for application as protective coatings for solid oxide fuel cells (SOFCs) interconnects. The coatings on bare steel were oxidized for different times of up to 101 h at 800 degrees C in ambient air. After 1 h heat-treatment, the metallic films had already converted to (Mn, Co)(3)O-4 oxide with a spinel structure. With increasing oxidation time, a Mn2O3 phase was also detected, independent of the thickness of the coatings. This phase formation was attributed to Mn ion enrichment in the coating. Cr diffusion and stresses in the thin coatings were also observed. Bare steel samples were also preoxidized for different durations to determine a suitable oxidation time to form a stable (Mn, Cr)(3)O-4/Cr2O3 oxide scale on their surface. Steel samples preoxidized for 100 h and coated with Mn50Co50 were subjected to time-dependent area specific resistance (ASR) measurements for 500 h. The ASR values obtained were 15 and 17 m Omega cm(2) for the substrate coated with 0.3 and 1 mu m Mn50Co50, respectively. Also, no Mn2O3 phase was present, and no Cr diffusion was detected in the thicker coating. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3240597] All rights reserved.