There will never be a commercial Magnesium Gigacasting

In the last few weeks, I have seen many rumours and plans to produce a Magnesium Gigacasting. The idea was shared and commented on a lot, so it reached me. According to the articles, the Magnesium Gigacasting weight savings is significant over its Aluminium counterpart.

Whenever I read these news stories, I thought, “What a terrible idea!” That is why I’m making another bold claim around the Gigacastings:

There will never be a Magnesium Gigacasting in Series Production!

I’m not saying that because it is not made of Aluminium, and I like to work with that material. I also don’t hold a personal resentment against Magnesium alloys. There is an overshadowing technical reason for it.

Magnesium HPDC parts are great

Magnesium HPDC parts are widely used in the automotive industry, and it is great that we have them. For example, all Mercedes-Benz steering columns are made of Magnesium. Many cars have interior dashboard brackets, center console holders and interior cross-beams. These Magnesium castings have good mechanical properties and are lighter than their Aluminium counterparts, and the tools to make these castings have 50 to 100% longer lifetimes. The biggest advantage of Magnesium is its vibration-dampening properties. The vibrations of an aluminium chassis have their specific natural frequency. In precisely that frequency range, Magnesium doesn’t transmit these vibrations well. That is why the ride in a Mercedes-Benz feels so smooth.

Where is the issue with Magnesium?

Magnesium is far from an easy-to-handle material. When exposed to oxygen, it starts to burn so heavily that water cannot stop it. As 95% of today’s Magnesium alloys come from China, there is a high supply risk, seen in massive price spikes of several 100%. Also, the material’s carbon footprint is terrible and above 25 kg CO2/kg Mg.

However, corrosion is the biggest downside and reason for making that claim. Corrosion is not a material property. It is the property of the overall system. For a corrosion system, you need two metals and an electrolyte. If one is missing, there is no corrosion, so we see all the Magnesium castings in the interior.

However, when making a Gigacasting, the Magnesium alloy is exposed to the outside, which completes the corrosion system. Magnesium is alone on the far left of the electrochemical voltage series. That means every other metal is further to the right and, therefore, more noble in comparison. The Magnesium alloy has no chance to avoid contact corrosion.

However, some may say, then let’s coat the Magnesium casting and seal it off from the environment. That plan works excellent for Aluminium and Chromate-Steels. They form a stable, impenetrable barrier for oxygen. The Magnesium oxide layer is highly brittle. One rock chip on the car and the coating falls off. That oxide layer is so sensitive that Mercedes-Benz, in their specification DBL-5011, even limited the minerals contained in the water you quench the part after casting.

These are the reasons, why I claim there will never be a Magnesium Gigacasting in series production!

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