metals

molybdenum

Corrosion protection for steel

Molybdenum (from Greek Μόλυβδος mólybdos for lead) is a chemical element with the element symbol Mo and the atomic number 42. It is one of the transition metals, in the periodic table it is in the 5th period and the 6th subgroup (group 6) or chromium group.

Molybdenum occurs mostly as molybdenite (molybdenum luster, MoS2). There is also wulfenite (yellow lead ore, PbMoO4) and powellite Ca(Mo,W)O4. Large deposits are found in the United States, Chile, China, Canada and Peru.

Most of the molybdenum is obtained as a by-product of copper production and only about 30% directly from molybdenum ores. All ores are mainly processed into ammonium heptamolybdate. This is converted into molybdenum trioxide MoO3 by calcining at approx. 400 °C. The latter is reduced in two stages by hydrogen to pure molybdenum powder.

Molybdenum recovery from scrap is close to 100% as there is no oxidation loss.

In small additions, it is used to harden and prevent steel from becoming brittle. More than two-thirds of the molybdenum produced is used to produce metal alloys such as ferro-molybdenum. The shortage of tungsten in World War I led to the increased use of molybdenum for the production of high-strength materials. To this day, molybdenum is an alloying element to increase strength, corrosion resistance and heat resistance.