Aluminium metal is a powerful reducing agent. It reduces the oxides of metals like iron and chromium to the metallic state upon heating.
`underset("Ferric oxide")(Fe_(2)O_(3)(s)) +2Al(s) to underset("Aluminium oxide")(Al_(2)O_(3)(s)+2Fe(l))`
`underset("Chromium oxide")(Cr_(2)O_(3)(s))+2Al(s) to Al_(2)O_(3)(s)+2Cr(l)`
The reaction is known as thermit reaction. It is highly exothermic in nature. As a result, the metal iron or chromium which is formed, is in the molten state. It can be used to fill the cracks in the railway tracks and also the cracks in the machine parts. This process is known as thermit process.
