Aluminum and How it is Made?
Aluminum is a shiny and silver, corrosion-resistant alloy that is light in weight and has high strength at low temperatures. Just like stainless steel, there is a thin layer of oxide on aluminum which is meant to protect it from the air so, which means it is non-reactive to air but if this layer is damaged or removed the aluminum can burn by reacting with the oxygen in the air. The thin layer of oxide prevents corrosion by hindering the diffusion of oxygen to the aluminum and stopping the corrosion. Aluminum is obtained by the process of electrolysis. It is the most cost-effective method to refine metals at the highest purity and usually, aluminum is obtained by using this technique. Aluminum is available in several Shapes, Lengths, Sizes, and Grades including the most commonly used 6061 Aluminum and 6063 Aluminum. Aluminum has the following characteristics:
- Corrosion Resistant
- Light Weight
- Reflective and Shiny
- Electric and Thermal Conductor
- Durable and lasts longer
- Sound and shock absorbent
- Non-toxic and odorless
- Higher Strength at low temperatures
- Attractive appearance
- Higher Ductility
- Ease of fabrication
Aluminum is used in different forms including angles, sheets, channels, wires, and beams which are used for manufacturing several products such as aircraft and automobile parts, window and door frames, plumbing accessories, batteries, traffic lights, electronic equipment, roofs and ceilings, support for different structures, and interior and exterior applications.
How is Aluminum Made?
Aluminum is made in four stages:
1. Aluminum Ore
Aluminum is found in rocks such as slate, granite, clay, and anorthosite. Bauxite is an important aluminum ore and is found in many parts of the world including Asia, Europe, South America and Australia.
The second stage is mining the aluminum ores by blasting the earth and extracting bauxite using heavy machinery. The aluminum extracted from bauxite is around 50% of the bauxite extracted from the rocks.
The next stage is refining bauxite using Bayer process which involves four steps:
- i) Digestion
Bauxite is ground and caustic soda is added and pumped into the tanks where heat, steam, and pressure are released which causes a reaction forming aluminum compounds and sodium aluminate solution. The impurities are removed.
- ii) Clarification
Sodium aluminate solution is then blown off the tanks and cooled down with the help of heat exchangers and transferred to tall silos.
- iii) Precipitation
Aluminum hydroxide crystals and sodium aluminate are mixed together which causes precipitation. At this stage, the aluminum gets solid and the remaining liquid and impurities are filtered out.
- iv) Calcination
At this stage, the aluminum hydroxide crystals are processed through a thermal treatment called calcination. All the impurities are removed and aluminum oxide is left in the form of white powder.
Aluminum is then extracted from aluminum oxide. This stage is smelting which involves the use of steel reduction pots containing molten electrolytes. To this aluminum oxide is added and molten aluminum is collected and poured out into the molds.