Question

a porous film is formed by action oxygen on metal

Answer 1

Oxygen present in atmosphere in absence of moisture directly attack the metalsurface at low as well as at high temperatures. However metals like Na, K, Li, Be, Ca, Mg etc are rapidly oxidised at low temperatures. ... During oxidation corrosion a thin layer of oxide film is formed on the surface of the metal.

Answer 2

HEYA,,,,,]


IT IS DUE TO THE PROCESS OF CORROSION...

CORROSION IS THE PROCESS IN WHICH THE METALS CAME IN CONTACT WITH OXYGEN AND GET OXIDISED...SO A NEW KIND OF SUBSTANCE FORMS ON IT..


FOR EXAMPLE WHEN MAGNESIUM RIBBON IS LEFT EXPOSED IN AIR FOR SOMETIME IT GET OXIDISED AND FORMS A LAYER OF MAGNESIUM OXIDE WHICH HINDERS BURNING...


HOPE HELPED...


AND ALSO MRK BRAINLIEST IF HELPED...