Problem 14 - A Complete Resource Book in Chemistry for JEE Main

Question

Removal to basic oxide from metal before electroplating is known as (a) poling (b) galvanizing (c) pickling (d) anodizing

Step-by-Step Solution

Answer

(c) pickling

Step 1: Understanding the Terminology

The problem involves various methods related to metal treatment before processes like electroplating. We need to identify the method used to remove basic oxides from metals before electroplating.

Step 2: Analyzing Options

Let's look at each option: (a) Poling - A method used in metallurgy to reduce oxides, particularly in copper refining. (b) Galvanizing - Involves coating metals with zinc to prevent rusting. (c) Pickling - This process removes oxides and scales from the metal before further processing like electroplating. (d) Anodizing - Typically involves adding an oxide layer, not removing it.

Step 3: Determining the Correct Option

After evaluating all options, pickling is clearly defined as the process that removes oxides from metal surfaces, making it the most relevant choice for removing basic oxides before electroplating.

Key Concepts

Pickling Process

The pickling process is an essential technique in preparing metal surfaces before further treatment or electroplating. It involves immersing the metal in an acid solution to remove any rust, scale, or oxides that have formed on its surface. This step is crucial as the presence of these substances can hinder the adherence and quality of electroplating.

Typically, solutions like hydrochloric acid or sulfuric acid are used due to their effectiveness in dissolving oxides. During this process, it’s important to carefully control the acid concentration and temperature to avoid excessive metal loss or damage.

Once the pickling process is completed, the metal should appear clean and bright, ready for the next stages of treatment. Proper rinsing is vital after pickling, as any residual acid left on the surface could lead to corrosion or impact the quality of subsequent metal processing.

Oxide Removal Techniques

Removing oxides from metal surfaces is a critical step in achieving high-quality electroplating results. The most common techniques include:

• Pickling: As mentioned, pickling involves using acid baths to dissolve oxides.
• Mechanical Abrasion: Techniques like grinding or sandblasting physically remove the oxide layer from the metal surface.
• Chemical Reduction: Reductive processes may employ chemicals or gases that convert metal oxides back to metals.

It's important to select the appropriate method based on the metal type and the extent of oxidation. For instance, softer metals may not withstand aggressive mechanical methods, while specific chemical processes might best suit certain metals.

Metal Surface Treatment

Metal surface treatment encompasses a variety of processes designed to enhance the durability, appearance, or conductivity of metals. Following the removal of oxides, the metal is ready for further treatments such as electroplating, anodizing, or coatings.

These treatments are critical in various industries, from automotive to electronics, where the quality of metal surfaces can impact performance and longevity. Surface treatment can improve:

• Corrosion Resistance: By adding protective coatings or layers.
• Aesthetic Appeal: Through polishing, plating, or coloring techniques.
• Electrical Conductivity: By applying conductive layers in electronic components.

Selecting the right surface treatment depends on the desired properties and application, ensuring that the final product meets the necessary specifications and functional requirements.