Engineering Materials·MCQ explained

When paint is applied in three coats, the first coat is known as:

Try it first: pick an option, then read the explanation.

Correct answer: B. priming coat
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The Three-Coat Painting System

A high-quality, long-lasting paint job, especially on new or difficult surfaces, is typically built up in layers. The standard professional system consists of three distinct coats, each with a specific purpose. This layered approach ensures excellent adhesion, uniform color, and maximum durability for the final finish.

Detailed Analysis of the Options

(a) under coat

Role: The undercoat is the second coat in a three-coat system. Its job is to build on the foundation of the primer, providing the main body of color and completely hiding the original surface. It creates a smooth, non-porous surface that is perfect for receiving the final coat.

(b) priming coat

Role: This is the correct answer. The priming coat, or "primer," is always the first coat applied to a properly prepared surface. Its primary function is not to provide color, but to act as a bonding agent. It seals the surface (preventing subsequent coats from soaking in unevenly) and provides a stable, adhesive layer for the following coats to grip onto. It is the essential foundation of the entire paint system.

(c) finishing coat

Role: The finishing coat, also known as the topcoat, is the third and final coat. This is the layer that is visible. It is formulated to provide the desired final color, sheen (gloss, matt, etc.), and resistance to weather, wear, and dirt.

(d) stopping

Role: "Stopping" is not a coat of paint. It is a surface preparation procedure. It refers to the process of using a filler or putty (like a stopper) to fill nail holes, cracks, and other minor imperfections in the surface *before* the priming coat is applied.

The Three Coats of Paint

Coat NumberNamePrimary Purpose
1st CoatPriming Coat (Primer)Adhesion and Sealing
2nd CoatUndercoatBuild color and hide the surface
3rd CoatFinishing Coat (Topcoat)Provide final color, sheen, and protection
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