Question

In the process of metallizing, which metal is used in present practice of painting of bridges in Indian Railways?
1. Zinc
2. Bronze
3. Copper
4. Iron

Answer 1

Correct Answer - Option 1 : Zinc

Concept:

Paints:

• Paints are applied on the surfaces of timber, metals, and plastered surfaces as a protective layer and at the same time to get a pleasant appearance.
• Paints are applied in liquid form and after some time the volatile constituent evaporates and the hardened coating acts as a protective layer.

Constituents of Paint:

The essential constituents of paints are:

1. Base
2. Vehicle
3. Pigment
4. Drier
5. Thinner

Base:

• It is a principal constituent of paint.
• It also possesses the binding properties.
• It forms an opaque coating.
• Commonly used bases for paints are white lead, red lead, zinc oxide, iron oxide, titanium white, aluminium powder and lithophone.
• Lead paint is suitable for painting iron and steelworks, as it sticks to them well. However it is affected by atmosphere action and hence should not be used as final coat. While zinc forms good base but is costly.
• Lithophone, which is a mixture of zinc sulphate and barytes, is cheap. It gives good appearance but is affected by daylight. Hence it is used for interior works only.