Aluminum

Winning

Bauxite, the rest form of aluminum, consists mostly of Al203 (aluminum oxide). Around 8.5% of the Earth's surface is covered with bauxite. This makes aluminum the most abundant element on Earth after oxygen and silicon.

The bauxite is brought into contact with hot caustic soda. The caustic soda reacts with the aluminum oxide present in the bauxite. This forms sodium hydroxide. The other components of the bauxite settle and are filtered so that a pure hydroxide remains.

The sodium aluminum hydroxide is then cooled, so that the aluminum hydroxide crystallizes and the caustic soda remains. The aluminum hydroxide is heated (calcined) and this is how aluminum oxide, also known as aluminum soil, is created.

Production
The aluminum oxide powder (aluminum soil) is heated together with cryolite. At a temperature of 1000 degrees Celsius, direct current is fed through the liquid. The aluminum soil has now been dissolved in the cryolite and is split again by electrolysis, releasing liquid aluminum and oxygen. The liquid aluminium is then transported away and transported to the foundry. There, it is cleaned and possibly mixed with other materials (depending on the quality that the aluminum should get). The mixed aluminium is used to make rolling slabs and press bars. These press bars and roll plates form the basis of most aluminium products.

Around 1000 kilograms of aluminum can be made from 4000 kilograms of bauxite.

Properties

‍Alloy
Compri Aluminium supplies various alloys, all of which have a number of properties in common. This grade of aluminum is unalloyed. The material is not thermally curable. Increasing the strength of the material is only possible by cold formation, which is associated with a decrease in stretch and deformability. The corrosion resistance is excellent under 'normal' conditions and can possibly be improved by technical anodising. When this alloy is in a soft glow state, it is perfectly malleable.‍

Corrosion
Pure aluminum and alloys that do not contain copper behave well in many environments. The copper-free alloys are therefore massively used in the construction world. Aluminum is also used regularly in other industries; aluminum alloys are an integral part of everyday life. One of the reasons for this is the corrosion resistance of the material. Different alloys are used in various environments. To increase corrosion resistance, for example, a surface treatment can be chosen.

Surface treatments
Aluminium can be treated in many ways. In the construction industry, however, only two surface treatments are used. These are anodizing and muffling.

During anodising, a chemical process reinforces the naturally present oxide layer on the material.

When powder coating, the aluminum is first chemically cleaned and degreased. After that, it is statically loaded. When the charged aluminum is sprayed with the negatively charged powder, the powder adheres to the products. The material then goes through a drying oven where the powder is converted into a strong layer of lacquer.

Deformability
Aluminum is very strong but, thanks to its positive properties, it is also easily deformable under the right conditions. This deformability makes it possible to produce extrusion profiles and tubes with almost any desired cross-section.

Melting point
Aluminium melts at a temperature of 660°C. The aluminium alloys have no melting point, but melt according to a melting process, which varies from alloy to alloy.