As we all know, the iron will begin to rust after a long time , and aluminum would rust like iron? The answer is no, because the chemical reaction is different, aluminum surface will form the oxide film.
In the process of aluminum processing, we can add other anti rust and corrosion metal elements, so that the effect of anti rust can be achieved. For example, the 3000 series aluminum alloy, manganese has a good anti rust function, so that the 3000 series of aluminum can be used as an anti rust aluminum. In the same way, the density of the aluminum plate is decreased (the density of magnesium is lower, but the strength is higher).
This film is usually very thin, it is only 0.00001 mm thick . In industry, in order to make aluminum products more durable, often to do a good job that aluminum products dipped in containing 20% sodium sulfate and 10% nitric acid solution, make the film more thick (anodic oxidation), but the film is afraid of acid and alkali, so the aluminum pot should not be used to cook. People often think the pan is not bright enough, always use the ash or sand to wipe. In fact, this is a very unscientific approach. why plant ash can well remove the aluminum pot “jacket”?
first, the friction , absolutely not rust metal does not exist in the world, but is conditions with different degrees of bale. Rusty iron is because they can not produce a protective layer, so more and more rust, so we often see dark rust. But aluminum is not so, it is born of rust on its surface, hinder the oxygen into the aluminum, the inside of the aluminum and therefore will not regenerate rust, this layer of rust has become a feature film, we call it alumina. Alumina has a feature that will be wiped away and soon will generate a new aluminum oxide layer and continue to play a protective role.
Second, the plant ash contains potassium carbonate, is an alkaline substance, can be dissolved by chemical oxidation film. But when you just wipe a layer of oxide film, an aluminum pan bright some, not long after, aluminum because no oxide protection and continue to oxidize, to put on a layer of oxide film, an aluminum pan is still gray. Although you pick up the ash cleaning every day, every day, to form an oxide film or aluminum. In this “tug of war”, the increasingly thin. Finally, the open “skylight” — leak. And the effort, and the pot broke.Haha,So it’s not worthy it.
So the aluinum plate can’t rust during use but produce the alumina to protect the plate to oxidize further.
