A novel process to synthesize the (Mn,Co)(3)O-4 spinel coating for protecting ferritic interconnect alloys used in solid oxide fuel cell (SOFC) stacks has been developed, which is based on thermal conversion of an electrolytically codeposited composite layer. Simultaneous electrolytic deposition of Co and Mn3O4 onto a Crofer 22 APU substrate resulted in a composite coating layer consisting of a Co matrix embedded with Mn3O4 particles. Thermal conversion of the as-deposited layer in air at 850 degrees C led to the formation of a dense and adherent (Mn,Co)(3)O-4 spinel coating on the substrate. The spinel coating was effective in blocking Cr migration and improving the electrical performance of the interconnect alloy. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3504102] All rights reserved.