Question

According to electrochemical theory of corrosion involves:

• A. cathodic dissolution of metal
• B. cathodic deposition of metal
• C. anodic dissolution of metal
• D. anodic deposition of metal

Answer 1

The correct option is A cathodic dissolution of metal

In corrosion $F{e}^{2+}$ get oxidised to $F{e}^{3+}$ which takes place on anode surface.

Anode: $Fe\left(s\right)\to {Fe}^{2+}+2e^{-}$

Cathod:$O_2+4H^{+}+4e^{-}\to {2H}_{2}O$

Overall:$2Fe\left(s\right)+O_2+4H^{+}\to 2{Fe}^{2+}+H_{2}O$

${4Fe}^{2+}+O_2+(2+4x)H_{2}O\to {2Fe}_2{O}_3.x{H}_{2}O+4H^{+}$

So,$F{e}^{3+}$ get deposited on metal surface.