Chemistry in the Aluminum Industry

At Rio Tinto, science is everywhere. From understanding where to find minerals in the Earth to making aluminum. We use science every day. We do a lot of chemistry in our work. Especially analytical chemistry. But what is analytical chemistry? And how do we use it to make aluminum?

Let's start at the beginning!

What is Aluminum?

You have probably heard of aluminum. It is used to make many things. Aluminum foil, beverage cans, car wheels, aircraft and even satellite parts.

You may also know that aluminum is a chemical element. It is found on the periodic table of elements. This silvery-grey metal is the most widespread metal on Earth. It is also the third most common chemical element, after oxygen and silicon.

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Shown is a colour photograph of hundreds of crushed drink cans.

The cans are packed tightly together and fill the whole image, edge to edge. They are printed in many different colours and designs. All of them have silver-coloured metal bottoms and tops with ring pulls.

Aluminum, on its own, is very rare in nature. It almost always combines with other elements to form compounds. 

The most common aluminum compound in nature is aluminum sulphate (Al₂(SO₄)³. This is often used to make small particles clump together in wastewater treatment plants.

Aluminum also combines with oxygen to form aluminum oxide (Al₂O₃). This compound is called alumina. Alumina is often made from an ore called Bauxite. Alumina is usually a white powder. It is used in many different chemical and manufacturing processes.

Alumina also occurs in nature as a mineral called corundum. Rubies and sapphires are types of corundum.

Did you know?

There are at least 300 different compounds that contain aluminum.

Why Use Aluminum?

Physical Properties

The physical properties of aluminum make it very useful. Aluminum is not very dense. This means that it is light for its size.

When evaporated  in a vacuum, aluminum can form a thin coating on objects. This coating reflects both heat and light. It is used on mirrors, helium balloons, packaging and toys.

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Shown is a colour photograph of brightly-coloured balloons packed closely together.

The balloons are inflated and shiny in the shapes of stars and hearts. One is silver, others are gold, green, red and purple. They take up the entire photograph.

Aluminum is a good conductor of heat. This means that heat passes easily through it. This is why it is used to make pots and pans.

It is also a good conductor of electricity. This is why it is used to make electrical transmission lines.

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Shown is a colour photograph looking up a power pole.

The camera is on the ground, looking up along a grey metal pole. Twelve different cables are connected to two crossbars at the top of the pole. The connectors look like forks with two or three tynes. The sky in the background is bright blue with fluffy white clouds.

Aluminum is also very malleable and ductile. This means it can be easily formed into different shapes, such as flat sheets and thin rods. It is the second most malleable metal and the sixth most ductile.

Chemical Properties

The chemical properties of aluminum also make it useful. Aluminum does not corrode easily. This means that it is not easily damaged by reacting with water or air.

Aluminum is not very strong on its own. This is why it is often combined with other metals to form alloys. Aluminum alloys of copper, manganese, magnesium and silicon are lightweight and strong. These are often used to build aircraft and other vehicles.

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Shown is a colour photograph of an airplane on a runway.

The airplane has a propeller and three wheels. It is a shiny silver-coloured metal. The nose is painted in a black and yellow chequered pattern. There is a white star in a black circle on the side, along with the letters SX and B. A pilot’s helmet is visible under a curved, clear canopy in the top of the aiplane. The land around the runway is flat with green grass and a row of trees at the horizon. The sky above is flat and grey.

Did you know?

The Convair B-36 Peacemaker bomber aircraft was so big that it was known as the "aluminum overcast." 

Aluminum in Industry 

Because it is so rare in nature, people were not able to get a sample of pure aluminum until 1845. This was when German chemist Friedrich Woehler isolated aluminum from aluminum oxide. But his method was very difficult and time-consuming. Scientists needed to develop new methods to produce aluminum on a larger scale.

In 1886, two scientists each found a solution. One was physicist Paul Héroult in France. The other was engineer Charles Hall in the United States. They both invented a process for breaking down alumina to produce aluminum. They didn’t work together, but somehow both discovered the same process independently.

They filed patents for their processes in the same year and became known as the “aluminum twins''. Their process, called the Hall–Héroult Process, is the basis for the aluminum refining today.

The Canadian aluminium industry is the fourth largest in the world. It produces 3.2 million tonnes of aluminium every year. And it has one of the lowest carbon footprints. As of 2023, Rio Tinto operates 5 aluminum smelters, 6 hydroelectric plants, and a Research & Development Center in Québec, along with a smelter and hydro facility in British Columbia. Rio Tinto employs 10,500 people across all its operations in Canada.

How It's Made - Aluminium or Aluminum (2016) How It's Made Archive (4:30 min.).

Where does chemistry fit in?

Chemistry is the science of matter and how it is transformed. Manufacturers transform matter a lot when they refine bauxite ore to make aluminum.

At each stage in the process, analytical chemists need to keep a watchful eye on what is happening. Analytical chemists specialize in the separation, identification, and measurement of matter.

Their work can include separating one type of matter from another. Like separating alumina from bauxite. It can also include Identifying the different compounds in a sample. When processing aluminum, it can include determining the quality of the finished product.

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Shown is a colour photograph of eight flasks filled with liquids.

The clear flasks are in two orderly rows, but the camera is at an angle, so they appear to tilt down to the right. Each flask is labelled “200 ml” in blue letters. Blue handwriting is also visible on the glass, but it is not readable. The flasks have blue, white or yellow stoppers. The liquid in the flasks on the right is transparent and slightly blue, while the ones on the left are clear

To do this, analytical chemists and technicians need specialized knowledge and skills. They need to know different ways to sample and analyze data. Sometimes they even come up with totally new ways to collect data.

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Shown is a colour photograph of three people in lab coats around a computer screen.

The people are wearing matching dark blue lab coats and light blue disposable gloves. Two are wearing clear safety glasses, and the one in the centre is wearing dark protective eyewear. All three are looking at the same computer monitor on a lab bench. One has their hand on the mouse, one is pointing to the screen, and the third looks on. The information on the screen is not readable.

They also use specialized equipment and instruments. Sometimes these are simple things like beakers and volumetric flasks. Other times they are high-tech equipment.

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Shown is a colour photograph of a large machine with metal, white and black components.

Two large structures that look like TV cameras are pointing down from each corner, toward something on a small, round platform in the centre. This platform is attached to the centre of several large silver and black concentric rings. These are mounted vertically. Loops of cables are visible behind and below these structures.

Chemical technicians use optical emission spectrometers to analyse the chemical elements in metals and alloys. They use x-ray diffraction analyzers to understand the physical properties and crystal structure of samples. Both of these instruments provide the measurements needed to produce aluminium at Rio Tinto.

Our teams of analytical chemists and chemical technicians help us use materials efficiently and sustainably. This cuts down on waste and greenhouse gas emissions. They also help us make sure our processes are safe. Finally, they help make sure our products are of the highest possible quality.

So, the next time you pick up an aluminum can, think of all the chemistry that went into making it!

Let’s Talk Science appreciates the contributions of scientists at Rio Tinto in the development of this backgrounder.