SOFC Protection Coatings Based on a Cost-Effective Aluminization Process

Fuel cells have emerged as a promising new technology for meeting the Nations energy needs. Of the various types, solid oxide fuel cells offer environmentally clean, quiet and highly efficient electricity and heat generation from natural gas and other hydrocarbon fuels. In solid oxide fuel cell systems, cost remains the most significant barrier to widespread commercialization and to achieve the aggressive cost targets requires the use of common stainless steels whenever possible. However, without protective coatings, air-facing steel surfaces oxidize and volatilize chromium that poison the fuel cell stack. Similarly, air/exhaust heat exchangers must be designed to prevent high temperature corrosion and chromium volatilization. The fuel facing metal surfaces also must be protected from catastrophic failure mechanisms related to oxidation (due to high steam content gas streams), and coking. In Phases 1 and 2, an aluminization coating tailored for the solid oxide fuel cell market was developed. The coating demonstrates excellent resistance to oxidation, chromium volatilization, and coking on a range of common stainless steels. Based on its demonstrated low cost and scalability, this coating technology could provide a cost break-through for solid oxide fuel cell developers, allowing them substitute conventional austenitic and ferritic stainless steel for nickel-based superalloys in applications where high temperature corrosion dominates material selection. In this Phase 2A project, barriers to customer acceptance of the coating technology will be removed through validation of coating lifetime performance in fuel cell stack and balance-of-plant demonstrations. The project will also continue to refine the down selected coating formulation to further improve coating stability for high temperature, highly aggressive environment applications. Outside of fuel cells the coating technology has broad applicability in other high-temperature industries such as power generation, coal gasification, natural gas processing, industrial biomass combustion], and chemical processing plants. Materials requirements are severe for these applications; components must be tolerant to long-term, high temperature exposure in harsh, corrosive environments. Cost-effective corrosion protection, such as this coating technology would, therefore, be highly attractive, enabling the use of common steels.