In an electrolytic set-up to protect iron from corrosion, the iron is…
In an electrolytic set-up to protect iron from corrosion, the iron is
A. made the cathode
B. made the anode
C. used with a metal of lower electropositive potential
D. initially coated with tin
Cathodic protection is used in the industry to coat iron with a corrosion resistant metal like zinc, offering a corrosion resistant iron.
During cathodic protection, the metal to be protected (iron) is made the cathode, while the sacrificial metal like zinc is made the anode. This is because metals (or hydrogen) in all cases of electrolysis are usually deposited at the cathode, while non-metals are usually given off at the anode.
The zinc anode dissolves into positively charged zinc ion which migrates to the negatively charged cathode where they will be deposited on the iron, forming a sacrificial protective layer.
Now for the right answer to the above question:
- Option A is correct. iron is made the cathode, hence the name – cathodic protection.
- Option B is incorrect. the sacrificial metal like zinc is made the anode, not the iron.
- C is incorrect. the sacrificial metal must be of higher, and not lower electropositive potential.
- D is not the correct answer. No, the iron is not initially coated with anything.
You may please note these/this:
- Apart from zinc, other more electropositive metals like magnesium and aluminum can also be used at the anode as the sacrificial metal.
- Read more on cathodic protection.
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/ culled from 2016 JAMB-UTME Chemistry past question 24 /