Question

"The iron object to be protected from corrosion is connected to a more active metal either directly or through a wire. The iron Object acts as cathode and the protecting metal acts as anode. The anode gradually disappears due to the oxidation Of the metal to its ions due to loss of electrons. Hydrogen ions collect at the iron cathode and prevent the rust formation. The iron Object gets protection from rusting as long as some of the active metal is present. Metals widely used for protecting iron objects from rusting are magnesium. zinc. and aluminium Which are called sacrificial anodes."

Q. Explain cathodic protection through above lines.

Answer 1

Dear Student,

$$\begin{gathered} \mathrm{In}\mathrm{the}\mathrm{above}\mathrm{lines},\mathrm{cathodic}\mathrm{protection}\mathrm{takes}\mathrm{place}\mathrm{by}\mathrm{connecting}\mathrm{iron}\mathrm{with}\mathrm{a}\mathrm{more}\mathrm{electropositive}\mathrm{metal}.\mathrm{For}\mathrm{eg}.\mathrm{Magnesium}\mathrm{is}\mathrm{more}\mathrm{electropositive}\mathrm{than}\mathrm{iron}. \\ \mathrm{E}{°}_{{\mathrm{Fe}}^{2+}/\mathrm{Fe}}=-0.44\mathrm{V} \\ \mathrm{E}{°}_{{\mathrm{Mg}}^{2+}/\mathrm{Mg}}=-2.37\mathrm{V} \\ \mathrm{If}\mathrm{we}\mathrm{connect}\mathrm{magnesium}\mathrm{with}\mathrm{iron},\mathrm{then}\mathrm{magneisum}\mathrm{will}\mathrm{act}\mathrm{as}\mathrm{anode}\mathrm{while}\mathrm{iron}\mathrm{will}\mathrm{act}\mathrm{as}\mathrm{cathode}.\mathrm{As}\mathrm{a}\mathrm{result}\mathrm{of}\mathrm{thus},\mathrm{magnesium}\mathrm{will}\mathrm{not}\mathrm{allow}\mathrm{the}\mathrm{oxidation}\mathrm{of}\mathrm{iron}\mathrm{and}\mathrm{thus}\mathrm{will}\mathrm{prevent}\mathrm{it}\mathrm{from}\mathrm{rusting}.\mathrm{Magnesium}\mathrm{will}\mathrm{undergo}\mathrm{oxidation}\mathrm{while}\mathrm{iron}\mathrm{will}\mathrm{undergo}\mathrm{reduction}. \\ \mathrm{Magnesium}\mathrm{will}\mathrm{protect}\mathrm{iron}\mathrm{untill}\mathrm{it}\mathrm{is}\mathrm{fully}\mathrm{oxidised}\mathrm{to}{\mathrm{Mg}}^{2+} \end{gathered}$$