Optimization of electrophoretic deposition technique to control doping and densification of protective spinel coatings for SOC interconnects

Manganese cobaltite spinel coatings have been reported to limit oxidation and Cr-evaporation from ferritic stainless steel interconnects in solid oxide cell stacks; however, the implementation of the functional properties of the base Mn–Co spinel coating and compatibility with the substrate can be pursued through the optimisation of the coating composition, as well as the deposition method and sintering profile. Electrophoretic deposition (EPD) allows to deposit homogeneous layers in few seconds on complexly shaped steel components; it also offers the possibility to produce in-situ doped coatings, avoiding time and energy consuming multi-step processes. In this work, various EPD suspensions are optimised to achieve a single step co-deposition of CuO, Fe2O3 and Mn1,5Co1,5O4 on Crofer 22 APU. Different Fe-Cu doped Mn–Co spinel are successfully obtained by controlling the precursors amount in the EPD suspension and subsequent reactive sintering, as proved by detailed SEM and TEM analyses. Improved functional properties of produced coatings are evaluated in terms of oxidation kinetics and area specific resistance. Both the iron and copper amount in the coating and the sintering process significantly influence the coating densification, with benefits to the protective properties and thermomechanical compatibility with the interconnect.