GATE 2024 MT – Question 62
A mild-steel pipeline is cathodically protected using zinc at current density 10 mA m$^{-2}$. Zinc required per square meter per year is ______ g (nearest integer). Given: Zn atomic weight 65 g mol$^{-1}$ and $F=96500$ C mol$^{-1}$ of electrons.
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Correct answer: 105 to 107
Explanation
For 1 m$^2$, $I=0.010$ A.
Taking one year as 365 days, $Q=It=0.010(365)(86400)$ C.
Zinc oxidation releases two electrons per atom.
Faraday’s law gives $m=QM/(2F)=0.010(365)(86400)(65)/(2\times96500)=106.21\ldots$ g.
The answer is **106 g**.