Electrodeposition of Cobalt-Manganese Alloy Coatings for Surface Modification of Metallic SOFC Interconnects
Authors: McCrabb Heather , Lucatero Savidra , Snyder Stephen , Zhang Hui , Liu Xingbo , Taylor E. J. 
Published: February 2020

Solid oxide fuel cells integrated with coal gasification technologies have the potential to advance the state of coal-fired power generation systems, however technical issues that deteriorate the SOFC performance over time must be addressed before wide scale implementation of the technology occurs. The shift from ceramic interconnect components to less resistive metallic interconnects has afforded manufacturing cost reduction, increased mechanical stack stability and increased cell output. However, the commonly used chromium containing alloys have been shown to poison other cell components and display chromia scale spallation, both detrimental to cell performance. ([i]). Numerous research articles have been published on the positive benefits of modifying the surface of the SOFC interconnect via application of a cobalt-manganese oxide spinel coating ([ii],[iii],[iv],[v]). Implementation of this coating at an industrial scale requires an inexpensive manufacturing process for coating the SOFC interconnects. Electrodeposition is one coating technology under consideration for deposition of cobalt-manganese alloy coatings that may subsequently be converted to cobalt -manganese oxide systems through thermal treatment at elevated temperatures in an oxidizing environment. Electrodeposition is widely considered an inexpensive, scalable, industrial manufacturing process capable of coating components with complex surface features such as the gas flow field features incorporated on the surface of metallic SOFC interconnects.

In this work, a pulse electrodeposition process is being developed and validated for coating metallic SOFC interconnects with a cobalt-manganese alloy. A single acidic sulfate based electrolyte containing cobalt and manganese ions, sodium gluconate, ammonium sulfate and boric acid is used to electrodeposit the alloy coatings. The pulse electrodeposition process has been scaled from 5 cm2 laboratory scale button cells to 115 cm2industrial scale metallic interconnects containing gas flow field features. The alloy composition is influenced and can be controlled by the electrodeposition parameters to tune the spinel composition. Long term exposure at elevated temperatures has shown that the coatings function as a barrier to chrome diffusion toward the surface with minimal increase in the area specific resistance (ASR) suggesting a well-adhered chromia scale. Long term on-cell performance tests using coated button cells displayed minimal voltage decay, indicating cell stability (Figure 1). Coating composition as a function of electrodeposition parameters, as well as performance data from short-stack testing will be presented.

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