Porous Film is also called as ‘Non protective Film’. Explain with an example.
In porous film, the volume of metal oxide formed is less than the volume of the metal from which it is formed. Hence this film possesses pores or cracks in the structure. Through these pores, atmospheric oxygen can enter and attack the metal. Hence it is non protective oxide film. Examples: Such type of oxide film is formed in alkali metals like Li, K, Na and alkaline metals like Ca, Sr, and Mg.