Iron is often galvanized in order to

Analysis

The question asks for the primary purpose of the industrial process known as galvanization when applied to iron.

Concept Explanation

Galvanization is a metallurgical process where a protective coating of zinc is applied to iron or steel.

• Why Zinc? Zinc is more reactive than iron. When iron is exposed to air and moisture, it undergoes oxidation (rusting). By coating the iron with zinc, we create a "sacrificial anode."
• How it works: Even if the zinc coating is scratched, the zinc will corrode in preference to the iron because it is more electropositive. This effectively prevents the iron underneath from rusting. This process is a common method used in Nigeria for protecting roofing sheets and iron pipes from the humid, corrosive environment.

Step-by-Step Solution

1. Evaluate Option A: Malleability is a physical property of metals. Galvanization creates a surface layer; it does not change the internal crystalline structure of iron to make it more malleable.
2. Evaluate Option B: Removing impurities is typically done during the extraction of iron from its ore (e.g., in a blast furnace), not by galvanizing the finished product.
3. Evaluate Option C: Corrosion is the gradual destruction of materials by chemical reaction with their environment (rusting). Since zinc prevents iron from reacting with oxygen and water, this is the primary purpose of galvanization.
4. Evaluate Option D: Rendering a metal "passive" refers to making it unreactive by forming a thin, non-porous oxide layer (like aluminum does naturally). Galvanization is an external coating process, not a passivation process.

Conclusion

The process of galvanization is specifically designed to prevent the oxidation of iron, which is commonly known as corrosion or rusting.

Exam Tip: Always remember the "Sacrificial Protection" concept. If you see a question about "galvanizing," immediately associate it with Zinc and Rust Prevention.