Research on the corrosion behavior and mechanism of high-aluminium 800H with pre-oxidation

The corrosion resistance of alloys is significant in the concentrated solar power plant (CSP). The maximum operating temperature of the existing nitrate heat storage system is 565 °C. The next-generation CSP requires a higher operating temperature of 600-800 °C to achieve the best efficiency. However, the subsequent nitrate decomposition will cause more severe corrosion to components such as alloy storage tank pipes. In order to enhance the high-temperature corrosion resistance and reduce the cost, Incoloy 800H, which has good high-temperature strength and oxidation resistance, can be selected as the application material for the next-generation CSP, and the cost is lower than that of the current commercial Inconel 625 alloy. In this study, Incoloy 800H was added with 3.33 wt.% Al and pre-oxidation treatment was carried out to investigate its corrosion behavior and mechanism in nitric acid molten salt at 650 °C. The results indicated that high aluminium 800H has excellent corrosion resistance in nitrate for 600 h. The pre-oxidized samples have a corrosion rate of only 24.5 μm/y after 480 h, which meets the international advanced standards for the lifespan of the next-generation CSP. The method of pre-oxidation at 1050 °C for 4 h can form a protective α-Al 2 O 3 layer on the surface and simultaneously form a spinel protective layer, enhancing the corrosion resistance through the inner and outer double oxide layers. This research is conducive to expanding the application scope of this alloy and enhancing the reliability and service life of industrial equipment. . 1High aluminium 800H has excellent nitrate corrosion resistance and its performance meets the international standards for next-generation CSP. 2. Pre-oxidation is mainly useful and benefit from the α-Al 2 O 3 protective film with spinel products. 3. Lack of Cr in the intergranular corrosion of the matrix, and the alloy elements diffusion behavior cause the corrosion. 4. The corrosion resistance mechanism of the inner and outer double oxide composite layer. Best Regards.