Uses of manganese
The main users of manganese are, or have been:
- the chlorine industry for bleach manufacture
- the steel industry
- other metallurgical applications
- other uses in the chemical industry
The industrialisation of the cotton industry in the late eighteenth and early nineteeth centuries required an industrial-scale method of bleaching cotton. The use of ‘bleaching powder’ (chloride of lime and other chlorine/calcium compounds) reduced the time taken to bleach cotton from months (bleaching in sunlight, later superceded by bleaching using suphuric acid) to hours. The manufacture of paper and soap also required bleach.
Commencing in the 1780s, chlorine for bleach manufacture was obtained from salt by reaction with sulphuric acid and manganese dioxide. This method declined towards the end of the 19th century in response to the introduction of chlorine production processes from the hydrochloric acid by-product of the Leblanc process (manufacture of sodium carbonate).
One of these chlorine production processes, the Weldon process, involved boiling hydrochloric acid with the manganese to produce chlorine and manganese chloride. (The remains of Weldon chlorine stills can be seen at Spike Island, Widnes.) Manganese was considered to be expensive by the chlorine industry and recovery processes for its reuse were developed [Twigg 2001]. One such recovery process involved treating the manganese chloride with milk of lime (a thin cream of slaked lime and water) to make ‘Weldon Mud’ or ‘Recovered Manganese’ (a mixture of calcium manganite CaO.2MnO2 and manganese manganite MnO.MnO2). This was separated from the calcium chloride solution and used again in the chlorine production process. [Gardner & Cooke 1971: 669]
Welsh manganese ores, in the oxide form, were used for these purposes in the chemical works around Glasgow associated with the cotton industry in the 19th century.
The steel industry
In Ancient Greece, the presence of manganese in the iron ore used by the Spartans is a possible explanation as to why their steel weapons were superior to those of their enemies. The same is also said of steel from Toledo, Spain [Chambers No. 659, 1876: 543–44]. At the beginning of the 19th century, both British and French scientists began considering the use of manganese in steelmaking, with patents granted in the U.K. in 1799 and 1808. In Germany in 1816 it was reported that manganese increased the hardness of iron, without reducing its malleability or toughness and in 1826 Prieger produced a ferromanganese containing 80% manganese. J.M. Heath produced metallic manganese in England in about 1840. The following year, Pourcel began industrial-scale production of "spiegeleisen", a pig-iron containing a high percentage of manganese, and in 1875 he started the commercial production of ferromanganese with a 65% manganese content. [IMnI] From 1848, Robert Mushet (1811–1891) experimented with spiegeleisn at the Darkhill Iron Works in the Forest of Dean. In 1856 he patented the Bessemer-Mushet process and produced the first steel for rail in 1857 [Thomas 1999]. In 1860 Bessemer used this work to develop his own steel-making process. In 1866, Siemens patented the use of ferro-manganese in steelmaking so as to control the levels of phosphorus and sulphur. In 1883 Robert Hadfield found that manganese steel (containing 13% manganese) combined great toughness and hardness [Fermor 1945: 41].
From the mid 19th century the use of manganese to improve the wear resistance and hardness of steel quickly became (and remains) by far its largest single use. At least 90% of world manganese ore production is used by the iron and steel industries [Dewey & Dines 1923: 49]. In the 1940s an average 14lb (6kg) of manganese was needed to make every ton of steel [Down 1980: 9].
There are three main applications for manganese in steel making:
- As a direct addition to the furnace charge of blast furnaces making basic iron; in this case the ore acts as a deoxidiser and desulphuriser. (It can also be used as a de-gassing agent in the crucible process of steel making.)
- As an alloy, in ferro-manganese, silica-manganese, and spiegeleisen.
- Ferro-manganese is usually made in a blast furnace. High grade ferro-manganese contains about 78% manganese, 8% carbon and the remainder iron but the alloys can contain 50–80% manganese, 10–42% iron, 5–8% carbon and 2% silicon. Ferro-manganese can be used as a deoxidiser in the open-hearth method of steel making and to provide a known quantity of carbon at the end of the conversion process in the Bessemer process of steel making.
- Silico-manganese is made in an electric-arc furnace and has 60–75% manganese, 20–25% silica and the rest iron.
- Spiegeleisen contains 10–35% manganese, 60–85% iron, 4–5% carbon and 1% silicon. Spiegeleisen can be used in the Bessemer process of steel making to provide a known quantity of carbon at the end of the conversion process.
- In the 1880s Welsh ore was calcined at the ironworks before being added to the blast furnace together with richer manganese ores. The result was an alloy containing about 45% manganese (mid-way between ferro-manganese and spiegeleisen) which was exported to the USA. [Halse 1887: 115]
- In the manufacture of manganese and other steels. Manganese steels contain 11–14% manganese (e.g. Hadfield’s Era steel with 12–13%). These steels have good resistance to wear and have particular applications such as railway crossings. Other steels such as steel rails have an appreciable manganese content: in 1933 more than 200,000 tons of steel rails were used in Britain. Formerly these contained .8–.9% manganese (equivalent to 1,600–1,800 tons of metallic manganese (about 2,500 tons of ore) but after 1918 this percentage was increased to 2% to give greater wear resistance. The corrosion-resistant Era steels contain .5–1.5% manganese (plus other metals such as chromium and molybdenum) and are used for forged pressure vessels. (See Chapman [1975: 54] for a more full discussion of the effects of varying amounts of manganese on the properties of steel.)
The Welsh ores were too low grade and too impure to allow them to be employed for ferro-manganese (although in the 1880s the ores were said to have been sent to Flintshire and Lancashire for this purpose) and hence their main value was as a direct addition to the blast furnace or for production of spiegeleisen.
Other metallurgical uses
Alloys of copper, tin, zinc, lead and nickel (i.e. brasses and bronzes) can have small percentages (.5–5%) of manganese added to them to form manganese brass, manganese bronze, manganese copper, manganese cupro nickel etc. These alloys have particular applications as bearing metals where the manganese generally improves wear characteristics. Manganese bronzes are also used where the non-magnetic and/or non-sparking properties of the material are important, for instance in non-magnetic tools.
Aluminium can have small amounts of manganese added to harden it. Duralumin (often referred to as ‘Dural’) is an age-hardening aluminium alloy containing 3.5–4.5% copper, .4–.7% manganese and .4–.7% magnesium [Chapman 1976: 61]. Jones & Gwyn [1989: 131] report that sheets of half-hard aluminium with a 1.25% manganese content were produced at the Dolgarog aluminium works during WW II.
Manganin, alloys containing 70–86% copper, 4–25% manganese and 2–12% nickel and 0–.3% iron, have a low temperature coefficient of resistance and is used for electrical resistances [Gardner & Cooke 1971: 400]. An alloy with 72% manganese, 18% copper and 10% nickel has a very high coefficient of expansion and is used for thermostatic bimetals [Young 1954: 385].
Manganese boron is used in the production of other alloys and manganese titanium is used for removing oxygen and nitrogen from copper alloys [Gardner & Cooke 1971: 399].
Manganese is used as a flux in smelting silver and lead ores. [Dewey & Dines 1923: 48]
Manganese dioxide is a constituent of Thermit™, an incendiary mixture of powdered aluminium and iron or manganese oxides, used for welding metals in certain applications such as continuous welded (railway) rail and earth electrode systems [Gardner & Cooke 1971: 622].
Manganese phosphating is used as a treatment for rust and corrosion prevention on steel.
The chemical industry
Manganese has a variety of medium and small scale applications in industrial chemicals such as manganese dioxide and potassium permanganate.
- Manganese dioxide MnO2 (manganese black, battery manganese). A heavy black powder; occurs naturally as pyrolusite. Used as a source of manganese metal for metallurgical use (as described above), as an oxidising agent, in glass manufacture (to remove the green colour caused by iron impurities), in Leclanché cells (such as non-rechargeable dry batteries), as a catalyst in the laboratory preparation of oxygen etc.
- Potassium permanganate KMn04. A deep purple crystalline soluble salt, dissolves in water to give a purple solution which acts as a powerful oxidising agent. Used as a disinfectant and in volumetric analysis.
Manganese is used in various pigments such as manganese black, manganese blue, manganese (Rosenthiel’s) green, manganese velvet brown (umber), manganese violet and manganese white. These pigments are used in the production of ceramics (pottery, tiles etc.), paints, and in calico printing (manganese bistre and manganese brown) [Gardner & Cooke 1971: 399–400]. A related use of manganese dioxide is as a drying agent in paints and varnishes to catalyse the oxidation of oils.
The use of manganese compounds as colouring agents is of considerable antiquity. Manganese dioxide was used as a pigment for cave paintings during the upper paleolithic period (40,000–12,000 BCE). The Egyptians and the Romans used manganese ore either to decolorize glass or to give it pink, purple and black tints. [IMnI] Pliny (first century CE) was mentions haematites magnes, a stone of blood colour which he distinguished from magnes (lodestone), in connection with glass making [Hoover & Hoover 1912: 586n]. Biringuccio [1540: 113] mentions manganese (in the form of pyrolusite) being used to colour glass and earthenware. Hawthorne & Smith [1979: 55n] discuss the coloration effects of manganese in medieval glass making in some detail.
Manganese is used a constituent of high pressure and temperature (e.g. steam applications) jointing compounds such as ROCOL® STEAMSEAL