Biomass embodies tremendous potential as a renewable energy resource. According to the biomass Thermal Energy Council (BTEC), biomass energy is renewable, carbon neutral, domestic and technologically mature. In addition, the low cost per BTU of wood chips and pellets relative to fossil fuels makes biomass an attractive thermal energy source. Furthermore, ~7% of global energy consumption comprises small-scale biomass combustion,[1] representing a tremendous market for technologies that facilitate enhanced biomass utilization. However, a major challenge associated with utilization of biomass is its combustion behavior. The moisture content, chemical composition, and combustion efficiency varies depending on the source of biomass. Small scale biomass combustors (Figure 1) which for cost reasons are often constructed of mild or low-alloy steels, during operation are subjected to corrosive environments which include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. There is a need to create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials. The materials used for cookstoves must improve burning efficiency, must be able to operate at higher temperatures, and should be low cost material systems to durably perform in the corrosive environments.

Within this context, Faraday Technology is working on developing low cost and high value corrosion-resistant alloy coatings for existing bio-combustors or lower cost steels with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of binary/ternary/quaternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate and subsequent accelerated high temperature corrosion evaluation. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and high-temperature corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, 100 wt% Cr, 7 wt% Co- 93 wt% Cr binary and 15 wt% Ni – 20 wt% Cr – 55 wt% Co (NiCoCr) ternary alloy coatings demonstrated enhanced corrosion resistance when exposed to an aggressive environment (~700°C, 1000 hr, coating surface salted with ~1 mg/cm² every 100 hours). When compared to the SS base material the Cr/CoCr alloy coatings exhibited effective protection to the substrate and over 10 times lifetime improvement to its base material.

Acknowledgements: The financial support of DOE Contract No. DE-SC0013870 is acknowledged.

[1] Biomass Production Now 10 Percent of World Energy, http://www.realclearenergy.org/charticles/2013/09/26/biomass_production_now_10_percent_of_world_energy_107257.html. Accessed 12 Jan 2015.