Background

According to the International Manganese Institute, manganese makes up about 0.1% of the Earth's crust, making it the 12th most abundant element on earth. It is the fourth most used metal in terms of tonnage, being ranked behind iron, aluminium and copper, with in the order of 46 million tons of ore being mined annually (2008).

Manganese process

Approximately 90% of all manganese consumed annually goes into steel as an alloying element. This is as silico manganese (SiMn), high carbon ferro manganese (HC FeMn) and refined ferromanganese (Refined FeMn). The balance is consumed in other applications such as chemical production, batteries and in other alloys such as aluminium alloys etc.

The manganese ferroalloy production process is indicated on the following chart.

Uses

Manganese has numerous applications which impact on our daily lives as consumers. The main uses are in industrial and metallurgical applications, batteries and chemicals.

Steel production

Manganese is essential to steel production by virtue of its sulphur-fixing, deoxidizing, and alloying properties. Manganese has played a key role in the development of various steelmaking processes and its continuing importance is indicated by the fact that about 90% of all manganese consumed annually goes into steel as an alloying element. No satisfactory substitute for manganese in steel has been identified which combines its relatively low price with outstanding technical benefits.

Aluminium alloys

Although ranking far behind steel, the second most important metal in which manganese plays an important alloying role is aluminium. Some 23 million tons of aluminium are produced annually. Small amounts of manganese are found in many of these Aluminium alloys, enhancing corrosion resistance. Intermetallic compounds, formed with iron and silicon, have an electrolytic potential which is far less negative than that of aluminium. This means that the aluminium surrounding such particles will be attacked under corrosive conditions, with disintegration further spreading as a series of deep pits are formed which spread the process to other particles. Manganese replaces iron-silicon compounds with manganese-iron-silicon compounds which have an electrolytic potential very close to that of aluminium. As a result there is no potential difference and therefore no corrosion.

Copper alloys

Manganese is probably the most versatile element which can be added to copper alloys. Small additions of manganese (0.1 to 0.3%) are used to deoxidise the alloy and improve its mechanical strength. Manganese has a high solid solubility in copper and in binary systems with copper and aluminium, zinc or nickel as the binary constituent. Many commercial copper alloys contain around 1 to 2% manganese to improve strength and hot workability. In order to reduce costs, manganese can replace part of the nickel in nickel-silver alloys.

Other metallurgical uses

Manganese is used in a number of other alloys such as titanium, zinc and is added to a number of alloys which are used for very specific applications, generally related to the electronic industry.

Batteries

After steel the second most important market for manganese, in dioxide form, is that of portable dry cell batteries. It is used as a depolarizer in dry-cell batteries. Dry cell consumption in the world exceeds 20 billion units per year. In the battery cell, the anode and cathode are essentially humid. During discharge, hydrogen generated at one of the electrodes coats the latter with a gas film, preventing any further wetting, hence cutting off electrical generation. The role of the manganese dioxide is to oxidize the hydrogen and form water. The rate at which this occurs depends on the reactivity of the dioxide.

Chemicals

Potassium permanganate

Potassium permanganate is one of the best known manganese products. It is a powerful oxidizing agent with bactericidal and algicidal properties, which enable it to be used in purifying drinking water and treating waste water. It is also used for odour control, including deodorization of discharges from paint factories, fish-processing plants, etc. Permanganate has a variety of other applications as an oxidant.

Agriculture

An important application for manganese is “Maneb” (manganese-ethylene bisdithiocarbamate), an organo-chemical compound sold in the form of a yellow powder. It is sold under different trade names as an agricultural fungicide and is widely used for controlling crop and cereal diseases, downy mildew in vines, scab in fruit trees, banana and peanut diseases among others. Some 200 000 tons of Maneb is estimated as a world-wide consumption figure. Manganese sulphate is widely used as an end product in fertilizers and animal feed, and as an intermediate product in the chemical industry.

Human Health

One vital feature of manganese, which is not widely appreciated, is its role as an essential element in maintaining human health. It is found in a number of medications. Recommended daily dietary intake levels have been established by US regulatory authorities in an effort to ensure the maintenance of good health.