Why does aluminium foil not burn?

Answer 1

Aluminum foil is composed of aluminum and aluminum alloys. For the simplest model, it can be considered a pure sheet of aluminum with a thin layer of aluminum oxide. The aluminum oxide layer is what gives aluminum foil its protective properties, and it forms spontaneously on contact with the oxygen in the air -- if you scrape it off, the layer will re-form immediately, much like the layer of chromium oxide in stainless steel. In the case of aluminum alloys, the layer has to be generated through other means, such as anodizing.

Burning (combustion) is an exothermic chemical reaction, typically a form of oxidation. In general, this just means that the oxygen from the surrounding air combines with the burning material (the fuel), causing the molecules that make up the fuel to break apart and release energy. Other highly-exothermic reactions may be referred to as "burning", such as thermal decomposition or reduction-oxidation (redox) reactions. For example, thermite is typically a mixture of iron (III) oxide and aluminum metal. When ignited, it appears to burn at a very high temperature; however, the actual reaction is a redox reaction that does not require the intervention of the oxygen in the air.

Because the outer layer of aluminum foil is already composed of aluminum oxide, there is little to oxidize. Aluminum oxide is stable far beyond normal cooking temperatures (it doesn't melt until over 2000C), making rapid thermal decomposition essentially impossible. The bulk of the material is aluminum or other metals, meaning it has nothing into which to decompose -- it is already the smallest unit normally achievable. Finally, because of the unreactive outer layer of aluminum oxide, other highly-exothermic reactions are difficult to achieve, especially at normal cooking temperatures. When aluminum metal is used in reactions, such as in thermite, the typical method is to reach its melting point. If you manage to reach over 660C (1220F) in your kitchen, the aluminum is probably the least of your worries.

Answer 2

Yes, aluminum foil is flammable, but it must be very hot for it to combine with oxygen and burn.

Answer 3

Yes the combustion point of aluminum is 4000 K°

Answer 4

The flammability of aluminum is considered to be very high. This element reacts with oxygen to form combustion which makes it a highly reactive and flammable material.