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

Question

Galvanization is applying a coating of? [2016] (a) \(\mathrm{Cu}\) (b) \(\mathrm{Zn}\) (c) \(\overline{\mathrm{Cr}}\) (d) \(\mathrm{Pb}\)

Step-by-Step Solution

Answer

Galvanization applies a coating of Zinc (Zn).

Step 1: Understanding the Question

The question is asking about the process of galvanization and what kind of coating is used in that process. The options given are metals: Copper (Cu), Zinc (Zn), Chromium (Cr), and Lead (Pb).

Step 2: Recalling Galvanization Process

Galvanization is a process where a protective zinc coating is applied to iron or steel, to prevent rusting. This is a widespread method used to protect metal from corrosion.

Step 3: Identifying the Coating Material

From the explanation of the galvanization process, it's clear that the coating material used is zinc. Therefore, in the options given, zinc corresponds to option (b) \( \mathrm{Zn} \).

Key Concepts

Zinc Coating

Galvanization involves applying a layer of zinc onto the surface of iron or steel. This zinc coating acts as a protective barrier. Here’s why zinc is such a star player in this process:

When zinc is applied, it doesn’t just sit on top like a lid on a jar. It actually bonds to the metal surface through a metallurgical reaction. This bonding creates a robust layer that adheres tightly, making it difficult for it to peel or flake off. Zinc is chosen for this job because it provides both physical and electrochemical protection.

Think of it like a shield. If the layer gets scratched or nicked, the zinc performs a heroic act called "sacrificial protection." Even when compromised, zinc will corrode instead of the iron underneath. This is because zinc is more reactive to environmental elements than iron, ensuring the core metal remains safe. Hence, adopting zinc in this role provides a two-layer benefit: barring physical contact and offering an electrochemical defense.

Corrosion Protection

The primary aim of adding a zinc coating through galvanization is corrosion protection. Metals do not like reacting with water and air because that can lead them to rust, especially iron and steel. Here’s how it helps:

• Barrier Protection: By creating a physical barrier, the zinc impedes moisture, airflow, and pathogens from reaching the metal surface. This is much like wearing a waterproof jacket during rain, preventing rusting and prolonging the metal's life.


• Sacrificial Protection: As mentioned before, zinc acts as a defensive layer that wears away first. By corroding before the iron, zinc does a valiant job of protecting the core metal from eventual deterioration.

The lifespan of the coating will depend on environmental conditions. For example, more aggressive environmental factors might consume the zinc faster, so routine checks and possible reapplications become crucial to ensure the metal’s longevity.

Iron and Steel Protection

Both iron and steel greatly benefit from galvanization, which is mostly done to prevent rusting, a common issue with these materials. Rusting can weaken structures, leading to expensive maintenance or even replacements.

Understanding why protection is necessary for these metals requires knowing a bit about their nature. Iron and its alloy, steel, are strong and widely used, including in construction and automotive industries. Yet, they can corrode when exposed to moist environments. Rust occurs when iron reacts with oxygen and water, forming iron oxide.

Using galvanization to apply a zinc coating effectively stops this natural decay process. Industries relying on iron and steel use this to enhance the durability and safety of their products. This way, they ensure that the structures or machinery remain in tip-top shape even in challenging environmental conditions.

Therefore, covering iron and steel with zinc is more than just a stabilizing extra—it’s vital for their performance and long-term sustainability.