When the wartime requirements stopped, the ability to produce magnesium and sell at a profit also stopped for many of the newer companies in all countries. So they closed and went out of business.
Most magnesium was used in pyrotechnics until the basic problems associated with producing castings (and other fabrications) were overcome. The property that made magnesium attractive for flares and tracer bullets created great problems in the foundry. Magnesium tends to oxidize readily when molten. Hence, the melting of magnesium alloys in an open crucible caused burning on the surface of the molten metal and the oxides formed would become inclusions in the sand castings made from the metal dipped from the crucible. Sand castings used water to bond the sand and this water would react with the magnesium giving burnt spots on the casting surfaces.
A German magnesium research group working at Bitterfeld discovered that carnallite salts could protect the surface of the melting magnesium (4). This cover flux also gave a refining action when stirred into the melt. Fused salt flux mixtures were designed and used to absorb the oxides, nitrides, and chlorides. This step was discovered in 1925 and it gave a process to produce very high-quality castings without inclusions (entrapped foreign particles). Sulfur and other chemicals were added to the sand to suppress the reaction with the moisture in the sand. Actual development of usable sand castings expanded commercially in the early 1920 period. After a long slow introduction, the use of magnesium in structural areas started as castings and grew to forging, extrusions, and rolled products, mostly in Germany. The development of magnesium use did not expand rapidly until the military build up of World War II started and new areas of use continued through the war.
The magnesium industry in the United States consisted of Dow Chemical alone from 1928 until 1940. While Germany and Japan were building up their magnesium industries in the 1930's, the U.S. and Canada were running pilot plants and looking at new technology. Henry J. Kaiser, the noted American industrialist was building a carbothermic magnesium plant in California. The plant used seawater magnesia (MgO) and coke as a reductant. Dow continued to operate their original electrolytic magnesium plant in Midland, Michigan. This plant used brine for the feedstock. In 1940, Dow also built a plant to produce magnesium from seawater in Freeport, Texas and operated this plant until December 1998. The first production of magnesium from seawater was in Great Britain in March 1940 when Magnesium Elektron used seawater magnesia to produce magnesium chloride. (5)
Germany had been the first into commercial electrolytic magnesium production. They continued research on this and on other magnesium production processes including the use of FeSi to reduce calcined dolomite. There was also extensive experimentation to develop the fabrication technologies, including sand casting, die-casting, forging, extrusion, and rolling. New alloys of magnesium were worked on to improve the properties of the metal. A complete summary of all the knowledge available about magnesium was published in 1939 in a book titled "Technology of Magnesium and its Alloys", by Adolf Beck. It was translated into English by F.A. Hughes in 1940.
The Germans, led by Dr. Gustav Pistor and Mosechel, worked to develop methods of extracting magnesium from carnallite. The chloride was loaded with hydroxyl groups. Mosechel decided in 1924-1925 to chlorinate the oxide at temperatures above the melting point of magnesium chloride. This produced a process to chlorinate calcined and raw magnesite with carbon and chlorine, to produce a truly anhydrous cell feed. To avoid importing magnesite into Germany, a process was developed in 1937 to treat local calcined dolomite with MgCl2 solutions available as byproducts from the potash industry.
Dr. Pistor and his staff also sought a way of reducing magnesium by a thermal process directly from dolomite. This was forerunner of the process developed by the Italians and by Dr. L. M. Pidgeon in Canada. The Germans used a rocking resistor furnace with internal electrical heating to give a temperature of up to 1400 °C , under vacuum. Furnaces were designed and built that gave a daily output of one ton of magnesium. In 1939, some furnaces of this type were built for the Italian Government and installed at Aosta, where they operated during the war.
In 1929, the British imported almost 60% of the total German magnesium production. This was used for commercial vehicle parts such as bus engines and transmissions.
The British had tried many ideas concerning magnesium production. In 1920, a new group took over the Magnesium Metal Company and its metallurgist E. A. Ashcroft. A plant was built using the Ashcroft process that was based on an electrolytic cell with a molten lead cathode. The magnesium was liberated from fused salt at the cathode producing magnesium-lead alloy. The pure magnesium was recovered from the lead alloy by subsequent salt bath electrolysis. The plant operated until 1923. (5)
In 1935, F. A. Hughes, through their managing director, Major CJP Ball, negotiated an agreement to acquire for the British Commonwealth the patents of I.G. Farben covering Pistor's process for thermal magnesium extraction, and formed Magnesium Elektron Ltd, as the operating company in which I. G. Farben and Imperial Chemical Industries were the other shareholders. In 1936, a works was built at Clifton Junction, Manchester, which was designed to extract 1,500 tons of magnesium metal per year from imported raw and calcined magnesite by the electrolytic process. In 1940, a further unit of 5,000 metric tons per year (mtpy) was built and started production in 1941. In 1942, the Government authorized MEL to erect a further 10,000-mtpy plant at Burnley. (5)
In 1935-1936, Murex Ltd built a 1,000-mtpy magnesium plant at Rainham that used calcium carbide to reduce MgO. In 1940, the Lancashire Metals Subliming Corporation tried to extract magnesium from calcined magnesite and calcined dolomite, under vacuum, using ferrosilicon as the reducing agent. The furnace was a high frequency induction furnace working at 500 kc/s. (5)
In 1938, the Magnesium Metal Corporation was formed in 1938 by the British Aluminium Co. and the Imperial Smelting Corporation to operate the Hansgirg patents for reducing calcined magnesite with carbon. A plant with the potential capacity of 1,000 mtpy of ingot was built at Swansea, Wales in 1939. (5)
The first electrolytic plants in the U.K. used imported raw and calcined magnesite from Greece, Yugoslavia, and India. From 1938, the supply was switched to magnesia obtained from seawater and dolomite. The British Periclase Co. was the first in the U.K. to treat seawater with calcined dolomite to recover both the magnesia from both the seawater and the dolomite. The magnesia obtained was of a highly reactive caustic type, well suited for chlorination to anhydrous magnesium chloride. In March 1939, M.E.L. first used magnesia from the British Periclase Co. and the metallic magnesium extracted was the first recorded commercial production from seawater.(5)
In the U.S., the American Magnesium Corporation (Alcoa) operated the fluoride process until 1927. Dow was the sole primary producer in the U.S. until 1941. Dow used the brines from Michigan to recover bromine, chlorine, sodium, and calcium. In 1940, Dow, advised by Dr. E. O. Barstow, decided to make use of the many natural advantages of Freeport, Texas to cheapen magnesium production costs and use seawater as the source of magnesium. Dow was producing 2,500 tons of magnesium in 1938, which was the total supply for both the U.S. and Canada.(5)
The Norwegian, Christian Backer, who ran the Canadian magnesium production at Shawinigan, went back to Norway and started De Norske Saltverker AS to produce magnesium and extract salts from seawater at Fotlandsvag outside of Bergen, Norway. The plant started operation in 1920 and reached a yearly capacity of 500 tons before it closed in 1922. Backer developed processes for the production of magnesium pistons and piston rods made in a permanent mold in a magnesium-aluminum-cadmium alloy. (6)
In Japan, in 1928, Mr. K. Nagayasu and Dr. R. Matsuura started research into the development of a magnesium production process at Ube in Yamaguchi Prefecture. In 1931, the Institute of Physico-Chemical Research built a magnesium pilot plant at Kashiwazaki, Japan. The first plant to produce the metal in commercial quantities was built at Ube, Japan, in 1933 by the Riken Metal Manufacturing Co. Magnesium production development was continued through the start of World War II. (7)
Magnesium development in Russia was accomplished after a great deal of scientific investigation. These investigations covered the physical-chemical properties of magnesium cell electrolytes; and the design and testing of magnesium electrolytic cells and other equipment. These studies were carried out between 1929 and 1936, under P.P. Fedotyev, P. F. Antipin, Yu. V. Baimakov, V. M. Gus'kov, I. G. Shcherbakov, S. V. Karpachev, and others. Technological processes for the production of magnesium were developed in fairly short time. In 1931, a magnesium pilot plant began operating in Leningrad and was used for the R&D work on the technical methods of production of anhydrous magnesium chloride, electrolysis, and casting and refining of magnesium. Work in this field was also conducted at the All-Union Aluminum and Magnesium Institute, and installations were designed for the first magnesium plants to be erected in the Soviet Union. (8)
After some administrative delays, the technology was transferred to Zaporozhye and to Solikamsk, and magnesium production plants were constructed at these sites. The first production was at Solikamsk in March 1936. The plant operations were improved and the plant reached its design capacity of 1,000 mtpy by the end of 1937. The Zaporozhye plant was a bit slower in starting up as the raw materials for the cell feed were not as pure as those at Solikamsk.
The S. A. pour la Fabrication du Magnesium in Switzerland produced magnesium in small quantities (500 tons per year) at its Martigny-Bourg plant from 1926 to 1947.