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Stainless Magnesium, Arsenic, Lithium and the Future

January 19, 2017

Magnesium is lightweight, strong enough for many vital applications, and easy to manufacture. Scientists are working to make it corrosion resistant, as well.

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Called the "metal of the future", magnesium is lightweight, strong enough for many vital applications, and easy to manufacture.

Magnesium is a very lightweight material – it weighs two-thirds less than aluminum, making it the lightest pure structural metal. It is strong enough to serve in many vital applications and is easy to shape and manufacture through many processes such as die casting. However, magnesium is very reactive and prone to corrosion. Therefore, it is not suitable for use in most environments, especially severe environments including humid and coastal areas with high water and salt contents in the ambient air.

Utilizing Arsenic to Poison Corrosion

It has been discovered that adding arsenic will reduce corrosion and allow magnesium to be used in new applications, such as the aerospace and automotive industries. The arsenic acts as a cathodic poison and in low levels retards corrosion by “poisoning” the corrosion reaction before it can come to completion. After adding around 0.33% arsenic to a magnesium alloy, corrosion was reduced by a factor of 10 when the material was placed in a salt solution.

Rheocasting

Another way to reduce corrosion in magnesium alloys includes changing the microstructure of those alloys. The lightweight alloys will allow the transportation industry to use those materials to decrease weight in vehicles and increase fuel efficiencies. In comparison, corrosion resistant magnesium products have been developed by coating the metal in the past.

After studying magnesium produced through rheocasting, Mohsen Esmaily discovered that its corrosion resistance is four times better than the same material produced through more conventional high pressure die casting. Researchers at Jönköping University developed rheocasting in order to increase the strength of magnesium alloys, but Esmaily discovered that the manufacturing method also increased the alloys’ ability to withstand corrosion.

Lithium for the Win?

Still another team of researchers have discovered an ultra-low density and corrosion-resistant magnesium alloy. They believe that this is the first step towards mass-producing “stainless magnesium” – a metal that combines the low weight and high strength of magnesium with increased corrosion resistance. This alloy uses lithium as a dopant and weighs half as much as aluminum and 30% less than pure magnesium. It achieves a higher corrosion resistance by forming a protective surface layer that functions in much the same way as the chromium oxide layer protects stainless steel from corrosion.

Using lighter materials allows for both energy savings and emissions reduction industries like the aerospace and automobile industries. In the future there will be a growing demand for corrosion-resistant magnesium alloys in not only the transportation industry, but also industries like the smartphone industry and other portable electronics industries.

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