What happens when an aluminium car body rusts?

What happens when an aluminium car body rusts?

We all know the reason why metal rusts, that is, metal exposed to air will be oxidised by oxygen in the air, and "rust" is the product of metal oxidation. In everyday life, we find that aluminium car bodies do not rust easily, why is this? In fact, it is not that aluminium does not rust easily, but that it is not easy to detect rust.

When iron rusts, the rust generated is loose and covers the surface of the iron, which is not only conspicuous, but also allows oxygen to enter and continue to oxidise the inner layer of iron until all the rusting of a piece of iron is finished. This is not the case with aluminium, which readily combines with oxygen to produce aluminium rust - aluminium trioxide, or aluminium oxide for short. Aluminium oxide is a thin layer of dense material, only 0.01 microns thick, which clings to the surface of the aluminium and prevents it from continuing to combine with oxygen. Therefore, we usually use aluminium products, should not use hard objects friction, so as not to damage the protective layer of oxide film.

Aluminium car body is a relatively active metal and even if the aluminium rust is removed, it will not take long for the oxide film to grow back. The aluminium rust is a dense oxide film, which protects the aluminium inside from reacting with the outside world, preventing the metal from continuing to corrode. If you have to remove the aluminium rust, you can use a weak acid or a weak alkali to scrub, now there are also special cleaning agents on the market to remove the aluminium rust, you just need to wipe with a rag on it, but after removing the rust is expected to soon be grey and long rust

The surface of the aluminium car body is usually galvanised to give it a zinc layer so that it can be protected against rust.