It may come as a surprise to many, even those who are already familiar with the Periodic Table, to find out that aluminum is actually one of the metals most chemically reactive to oxygen. While the alkali metals (lithium, potassium, cesium etc.) oxidize in open air so quickly that you can see a freshly cut piece tarnish while you count off just a few Mississippis, aluminum does so nearly instantly - thousands of times faster than the blink of an eye! But… this can’t be, you say, as you recall many samples of polished aluminum holding their luster forever. Well, the strange thing is that aluminum rust is transparent.

Wait, whaaaat?

Yes, aluminum oxide is better known as rubies and sapphires which without tiny contaminants is as colorless and see-through as ordinary glass. That you see metal instead of a gem when you look at your kitchenware is due to the fact that this oxide layer is extremely thin; four nanometers, to be exact. Effectively, the thickness of a single molecule. The resulting sheet is so tightly interlocked that it prevents any more oxygen from getting through and the oxide’s chemistry is so stable that it rebuffs almost anything else that it comes in contact with, thus preserving its integrity. This is why metallic aluminum is found everywhere in our modern life. The alkali metals on the other hand do not form protective oxide networks and thus quickly succumb unless carefully protected.

With an estimated global production of over 60 million tons, aluminum is the second most manufactured metal after steel and the rate of production continues to increase at a rapid pace as more and more uses are found for this light and easily recycled resource.