Problem 180 - A Complete Resource Book in Chemistry for JEE Main

Question

Galvanization is applying a coating of? (a) \(\mathrm{Cu}\) (b) \(\mathrm{Zn}\) (c) \(\mathrm{Cr}\) (d) \(\mathrm{Pb}\)

Step-by-Step Solution

Answer

Galvanization involves applying a coating of Zn (Zinc), so the answer is (b) Zn.

Step 1: Understanding Galvanization

Galvanization is the process of applying a protective zinc ( Zn ) coating to steel or iron to prevent rusting. This coating of zinc acts as a barrier that protects the underlying metal from corrosion.

Step 2: Identifying the Correct Element for Galvanization

Given the options, we need to choose the element that is used for galvanization. Since galvanization uses zinc to protect other metals, we identify this from the options.

Step 3: Selecting the Correct Answer

There are four options given: (a) Cu (Copper), (b) Zn (Zinc), (c) Cr (Chromium), and (d) Pb (Lead). From our understanding of galvanization, the correct answer is Zinc, i.e., (b) Zn .

Key Concepts

Corrosion Protection

Corrosion is a natural process that gradually destroys metals by chemical reactions with their environment. The most common form of corrosion is rust, which primarily affects iron and its alloys. This is where corrosion protection comes in.
One of the primary methods to protect metals from corrosion is through the application of protective coatings. These coatings can act as physical barriers preventing exposure to elements that cause rust, like air, moisture, and salts.

• Paints and varnishes provide basic barrier protection but may not be suitable for heavy-duty use where high resistance is needed.
• Sealers and waxes offer additional protection against moisture and corrosive elements.

However, not all coatings are created equal. Galvanization, specifically, uses zinc coating, which offers both physical and sacrificial protection.

Zinc Coating

Zinc coating, or galvanization, is a method that applies a protective layer of zinc to iron or steel. The zinc coating is beneficial for several reasons. It protects the underlying metal by forming a physical barrier against environmental elements like moisture and oxygen, which can cause rust.
Additionally, zinc offers sacrificial protection. It acts as an anode and will corrode instead of the steel or iron beneath it.

• This is because, in the electrochemical series, zinc is more reactive than iron, meaning it will corrode first, thereby protecting the metal beneath.
• Over time, even if the zinc layer is slightly damaged, it continues to offer protection to the underlying material.

Thus, zinc coating is highly effective in providing long-lasting protection against corrosion.

Metals and Alloys

Understanding the composition and structure of metals and alloys is essential for appreciating why methods like galvanization are important. Metals like iron have a crystalline structure that is particularly vulnerable to corrosion when exposed to air and moisture.
Alloys, which are mixtures of two or more elements where at least one is a metal, often perform better than pure metals when it comes to strength and resistance to depletion. The addition of other elements can change the properties of the metal significantly.

• For instance, adding carbon to iron forms steel, a much stronger material.
• Similarly, alloys like stainless steel contain chromium, adding both strength and additional corrosion resistance. However, even these materials can benefit from further protection through processes like galvanization.

By using zinc coatings, the longevity and integrity of these metals and alloys are enhanced, ensuring their usefulness in various practical applications.