This technology aims at using a corrosion product that forms at the interface between Li and structural materials as an insulating layer. By careful control of the corrosion reaction, the insulation layer can be formed uniformly on the inner surfaces of complex components. The corrosion layer may also be formed on the cracked area of the coating, thereby repairing insulation defects. The in situ coating with CaO and AlN have been studied in the United States11 and the Russian Federation,12 respectively.

Figure 3 Schematic illustration of the mass transport for in situ oxide coating in Li. Ov: oxygen in vanadium substrate; MLi: metal doped in Li for producing oxide coating.

A CaO insulator layer forms during the immersion of vanadium alloys in Ca-doped Li. For enhancing this reaction and stabilizing the layer, the O level in the alloy was increased by prior doping. The pro­cess is schematically shown in Figure 3. Careful control of the Ca level in Li and the O charging condition of the vanadium alloys made in situ for­mation and healing of the CaO coating possible at <500 °C. Because of the successful demonstration, in situ CaO coating was adopted as the means to mitigate the MHD pressure drop in the ARIES-RS power plant study.1

This technology was, however, shown to be inap­plicable at temperatures exceeding 600 ° C because of the unacceptably short lifetime of the coating induced by increased dissolution.2