Novel Corrosion and Erosion Preventive Amorphous Alloys Coatings

Solar energy is the most potential renewable and sustainable energy source. To achieve high solar-to-electric conversion efficiency and enable cost competitiveness with conventional methods of electric power generation, the next generation of Concentrated Solar Power (CSP) systems is expected to operate at temperatures above 700°C. Molten chloride salts are identified as a highly promising heat transfer fluid and thermal energy storage media capable of operating between 550°C and 750°C. These molten salts introduce a set of technological and engineering challenges because of their very corrosive characteristics for typical materials. In the proposed project, LM Group Holdings, Inc. propose to develop and apply amorphous alloy coatings with high corrosion resistance that will be able to withstand severe environment under molten chloride salt conditions and improved surface characteristics for different parts of the molten salt systems such as impeller, sealant etc. to be able to operate these systems at temperatures above 700C. Amorphous metals are a novel class of materials that have a disordered, non-crystalline, glassy structure. Due to their unique microstructure, amorphous metals combine ultrahigh strength, high hardness and ductility in one single material. Amorphous Metals are more corrosion resistant compared to conventional metals due to the lack of long-range periodicity, related grain boundaries and crystal defects such as dislocations and their compositions. Three different fully and partially amorphous thermally sprayed coatings were generated and optimized to obtain dense and uniform coating microstructure. The optimized coatings were sprayed on Haynes 230 alloy and study regarding their resistance against molten KCl-MgCl2 salt corrosion at 750C for 300 hours. Static capsule exposures were performed on Alloy 230 samples with and without coatings. Uncoated samples experienced intergranular attack and chromium depletion with a median depth of 34 µm. Coated samples experienced no observable attack on either the metal substrate or in the coatings. The lack of Cr depletion in the coatings is a very promising finding that merits additional study to determine the mechanism. This proposed project will build on LMGH’s extensive prior experience with amorphous metals-based coatings for different applications. LMGH along with ORNL and Sandia CSP facility work to understand the protection mechanism of novel amorphous metal-based coatings under severe corrosive environments and evaluate the corrosion resistance and mechanical integrity for CSP system components under real conditions. Commercial Applications and Other Benefits: The coating solution developed under this program would enable rapid adoption and wide-scale commercialization of CSPs which would effectively help the word transition from coal, oil and other fossil fuels to cleaner, more responsible renewable fuel. The scheduled projects under development for numerous solar thermal power plants using CSP technologies are indicative of market growth between now and 2019, at which time the market is expected to grow significantly at a CAGR of 60.2%, from $3 billion to nearly $25.8 billion.