RAS question
Galvanization is the process of coating iron with a thin layer of which metal to prevent rusting?
Correct answer: (A) Zinc.
Galvanization prevents rusting by coating iron or steel with a thin protective layer of zinc.
Explanation
Galvanization is the method used to protect iron and steel from rusting by covering them with a thin layer of zinc. NCERT lists galvanising among the standard ways to prevent corrosion, along with painting, oiling, greasing, chrome plating, anodising and alloying. The key point is that the protective metal in galvanization is zinc, not just any shiny or corrosion-resistant metal. This coating works well because zinc behaves as a sacrificial anode, so it corrodes preferentially and protects the underlying iron through cathodic protection even if the coating is damaged. That is why the NCERT passage notes that a galvanised article remains protected against rusting even when the zinc layer is broken.
Why the other options are wrong
- (B) Aluminium coating is associated with aluminizing or anodising, whereas galvanization specifically means coating iron or steel with zinc.
- (C) Tin coating is tinning, not galvanization, so it does not name the zinc layer used for galvanised iron or steel.
- (D) Copper coating is copper plating, while galvanization is defined by a zinc coating that protects iron and steel from rusting.
Concept
This tests corrosion prevention under the metals and non-metals part of basic chemistry. It recurs in RAS because everyday applications such as rusting, alloying and protective coatings are standard ways to connect chemistry with practical technology.