nitric acid renders iron passive by forming which compound?

Question

Dear person, in my chemistry textbook it is written that when iron is dipped in concentrated nitric acid, then iron is rendered passive due to the formation of an oxide coating on it; MY qs. is
1) what is the name and formula of that iron oxide.
2) Will nitric acid render all metals passive like iron by forming an oxide layer over it. If no,then what is the reason?
... thanks , swati

Answer 1

Fe2O3 is the most likely oxide - iron(III) oxide. Exactly the same happens to aluminium, and I'm sure a lot of other metals.

Nitric acid is not normally added to metals due to the poisonous oxides of nitrogen which are usually given off.