chemical bonding

[chemistry123456]

1) Aluminum reacts with oxygen in air to form aluminum oxide. Unlike rust, which flakes off, aluminum oxide remains bound to the aluminum metal, forming a protective layer that prevents further reaction. What might account for the difference in behavior between iron (iii) oxide and aluminum oxide and their respective metals?

2) What is this difference in properties of iron and iron (iii) oxide, in terms of the type of bonding in these substances.
________
Airsoft Powered Guns (http://airsoft-shop.info/tag/powered-guns)