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 Al alloys, enhancing corrosion resistance. The explanation for this beneficial effect is simple. 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 corrode 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.

Manganese is used as an alloying element up to its solubility limit of about 1.5%. Aluminium-manganese alloys and aluminium-manganese-magnesium alloys, which have been sold under different trade names, have found applications in such diversified areas as kitchenware, roofing, car radiators and transportation. By far the most important use of aluminium-manganese alloys is for beverage cans, of which some 100 billion units are produced each year. The market for aluminium-manganese cans has grown steadily, thanks to the fact that such cans can be recycled.

Aluminium alloys containing up to 9% Mn have promising properties, but they cannot as yet be economically produced. Technologies to produce these commercial “amorphous” metals through very fast cooling are of potential interest but the processes used are still very expensive and can only be applied to high value materials used in the aerospace industry.