Porous film is also called as Non protective film. Explain with an example.
1 Answer

Monovalent metals like Li, Na, K react with Oxygen & results in the formation of $Li_2O$, $Na_2O$, and $K_2O$.

Here of Oxygen is less than volume of Metal. The film developed over the surface is stable porous.

Corrosion is moderate, oxygen is insufficient to cover the surface. Corrosion continues through cracks, Pores & portion which is free from cracks & pores is protected.

Bivalent metals like Ba, Sr, Ca results in the formation of $BaO$, $SrO$ & $CaO$. In these cases also corrosion is moderate as film developed is porous stable

Please log in to add an answer.