Why is titanium only malleable when hot?

Why does iron corrode, while titanium doesn't? (No homework, will award 10pts)?

• Some facts I found on the net: TITANIUM: ----------------- *Density: 4.506 g/cm³ *Electronegativity: 1.54 (Pauling scale) *Atomic radius 147 pm *Covalent radius 160±8 pm *Crystal structure: hexagonal *Magnetic ordering: paramagnetic *Titanium reacts with air and water, passivly forming a strong oxide coating (TiO2). Once it gets damaged (due to a scratch e.g.) the layer regenerates too fast for the 'central' metal to corrode. *The only way it will corrode (from what i've researched) is from very strong and concentrated acids. TITANIUM DIOXIDE: ----------------------------- *Density 4.23 g/cm3 * http://en.wikipedia.org/wiki/Titanium_dioxide#Occurrence IRON: --------- *Density: 7.874 g/cm³ *Electronegativity: 1.83 (Pauling scale) *Atomic radius: 126 pm *Covalent radius 132±3 (low spin), 152±6 (high spin) pm *Crystal structure: body-centered cubic *Iron reacts with oxygen in the air to form various oxide and hydroxide compounds; the most common are iron(II,III) oxide (Fe3O4), and iron(III) oxide (Fe2O3). * http://en.wikipedia.org/wiki/Iron(II,III)_oxide * http://en.wikipedia.org/wiki/Iron(III)_oxide Now the question: Why does the oxidelayer on titanium stay firmly attached (making it very useful for submarines and airplanes etc...), while the oxidelayer on iron 'drops off' making it rust? I will award 10 points to the person who can clearly make me understand why this happens. This is no homework, I was wondering about this after I saw a documentary.

• Answer:

  Titanium atoms have a stronger bond.