The fourth in a series of NASA-AEC Liquid-Metals Corrosion Meetings, held October Z-3, 1963, was devoted to discussion of the mechanisms of liquid-metal corrosion, the results of compatibility tests with alkali metals, and the problems related to compatibility testing with alkali metals.
The fourth in a series of NASA-AEC Liquid-Metals Corrosion Meeting held October 2-3, 1963, was devoted to discussion of the mechanisms of liquid-metal corrosion, the results of compatibility tests with alkali metals, and the problems related to compatibility testing with alkali metals. Previous meetings in this series dealt with a broader range of topics that include mercury corrosion, liquid-metal analytical chemistry, and liquid-metal properties. In the interest of comprehensive coverage, this meeting was restricted in scope. It was felt that topics not covered could be deferred to meetings under other auspices planned for the near future.
Corrosion of containment materials is the most serious problem in liquid-metal systems. Most high-temperature engineering metals such as refractory metals, nickel-base and cobalt-base superalloys, and the austenitic and ferritic stainless steels are sufficiently resistant to liquid sodium and NaK to be useful up to about 1600 F. The most important factor in the corrosion of these materials under given conditions of temperature and flow rate is the oxygen content of the sodium. No material is truly corrosion resistant to lithium, although the refractory metals tantalum, columbium, and molybdenum do have some potential for high-temperature service in engineering applications. Zirconium and pure iron may also find some limited use in lithium, especially in lower temperature, twocomponent, static systems. The cobalt- and nickel-base alloys are unsuitable for high-temperature service in liquid lithium. The nitrogen content of the lithium is a particularly important factor. Potassium, rubidium, and cesium are somewhat less corrosive than the other alkali metals. The refractory metals and alloys are little affected by these liquid metals. The sliding and bearing properties of metals are generally affected adversely by the presence of pure molten metals. (Author).
This memorandum deals with the use of liquid metals in advanced spacepower plants. The principal liquid-metal candidates for such applications are mercury, NaK, potassium, lithium, cesium, and sodium. These metals are used primarily as heat-transfer media and as working fluids at high temperatures. This memorandum identifies specific areas for molten metal use and discusses the materials, problems, and developments associated with their containment. (Author).