Argon (Ar) – part of a series on gases used during the physical vapour deposition (PVD) process – an innovative method for improving the performance of stainless steel

Argon (Ar) is a chemical element with an atomic weight of 1. On the periodic table, argon sits between chlorine and potassium – atomic number 39.948.

Argon is one of the noble gases meaning that it is non-reactive and tends not to mix or bond with other elements. Argon is inert and the name comes from the Greek word, ‘argos’ meaning inactive or idle. The other noble gases classified as inert are helium, neon, krypton, xenon and radon.

Argon in the Earth’s atmosphere

Argon is the third most prevalent gas that makes up our atmosphere on Earth. It makes up 0.93 per cent of the air we breathe. Even at a puny 0.93% percentage by volume, this adds up to an enormous 66 trillion tons which is 1.3% of the Earth’s atmosphere by weight. Most of the Earth’s argon is radiogenic argon-40 and is generated by the decaying process of potassium in the Earth’s crust.

A photograph of the Earth’s atmosphere from space. Argon is one of the gases that form this protective layer to the planet more commonly known as air.

A photograph of the Earth’s atmosphere from space. Argon is one of the gases that form this protective layer to the planet more commonly known as air.

Britain’s first-ever Nobel prize winner for chemistry, Sir William Ramsay (1904), discovered four of the six noble gases – argon, neon, krypton and xenon. Sir William isolated argon in the year 1894 along with Lord Rayleigh, the first-ever British winner of the Nobel prize for physics (1904).

Applications for argon

In industry, noble gases are used in processes that require an inert atmosphere. For example, argon is typically found inside fluorescent and incandescent light bulbs where it is used to stop oxygen damaging the bulb’s hot filament.

A photograph of an incandescent light bulb. Inert gases like argon are used inside the bulb as unlike oxygen they are non-reactive and protect the lamp’s filament from damage.

A photograph of an incandescent light bulb. Inert gases like argon are used inside the bulb as unlike oxygen they are non-reactive and protect the lamp’s filament from damage.

Argon has also been found useful as humans look for ways to make products more energy efficient. Double glazing manufacturers that use argon to fill the air gap in double glazed windows have discovered that, although argon costs a little more, it has the benefit of decreasing the U-value of the units by 30 per cent. The U-value is the thermal transmittance of a material and, counter-intuitively, a lower score is better than a higher rating often leading to confusion! Using argon adds around 5% to the cost of producing window units.

Argon and stainless steel production

The single most significant use for argon is in the production of stainless steel and other high-grade metal alloys. Argon oxygen decarburisation (AOD) is a process used in the stainless steel mill to reduce the carbon content of the product.

In 2018, worldwide production of stainless steel was a staggering 50 million tons. Even at this level, stainless steel only accounts for approximately 5% of total steel production.
Output of stainless steel is generally predicted to rapidly increase in the next decade, with the focus of this new production being Far East markets. It is a relatively environmentally friendly product as most of the stainless steels produced today with modern methods contain approximately 60% scrap metal.

Stainless steel products, parts and components to be recycled. Modern manufacturing processes utilise a high proportion of stainless steel scrap metal in new products.

Stainless steel products, parts and components to be recycled. Modern manufacturing processes utilise a high proportion of stainless steel scrap metal in new products.

Argon in the PVD process

Double Stone Steel uses minuscule amounts of argon gas in the physical vapour deposition (PVD) process. We inject these tiny quantities of argon into our vacuum chambers to enable us to colour stainless steel sheets and profiles for our products. These chrome coloured stainless steels are vastly less harmful to the planet than traditional electroplating methods.

By Daniel Groves
Richard Storer-Adam is MD of Double Stone Steel Ltd which fabricates PVD coloured stainless steel. Richard’s background is in design and project management, he lives in Spain and travels extensively writing about writes about architecture and sculpture in Richard is passionately interested in sculpture.