SOFC Protection Coatings Based on a Cost-Effective Aluminization Process

To make SOFC systems more manufacturable and reduce costs, lower cost stainless steels have been substituted into the stack design wherever possible, including as alternatives to traditional ceramic interconnects within the stack and high-cost nickel-based superalloys in balance of plant (BoP) components. However, for successful implementation of these steels, protective coatings are necessary to protect the air-facing metal surfaces from high temperature oxidation and to minimize Cr volatilization from the metal, because Cr volatiles poison the cathode and degrade cell performance. In addition, on the fuel side of the system, carburization and coking are potential corrosion mechanisms for metals facing high carbon fuel streams. In this proposed Phase I SBIR effort, NexTech Materials will develop a low cost aluminization process, to apply protective aluminide coatings to metallic components. To demonstrate the applicability of the process to SOFC applications, two commercially important systems will be investigated. First, compatibility of the aluminide coating with SOFC stack components will be evaluated, including interactions with sealant materials and other cell components. A complete interconnect coating solution will be demonstrated by integrating the aluminide coating with the existing MCO active layer coating. The performance of these dual MCO/aluminide coated interconnects will be validated through three cell stack tests. Second, the high temperature corrosion protection and chromium volatilization mitigation of aluminide coated BoP components will be evaluated. Based on an analysis of cost and performance the commercial potential of the aluminization process for providing protective aluminide coatings for both the non-active seal area of metallic interconnects and BoP components will be quantified. The proposed project will build upon encouraging preliminary results to develop a commercially viable aluminization process that is amenable to high volume SOFC manufacturing. This work will leverage NexTechs commercial process technology for applying conductive oxide protective coatings to ferritic steels a process that has already been translated from the laboratory to pilot scale manufacturing at NexTech. It is anticipated that this experience will expedite commercialization of the aluminization process.