Page 147 - CITS - Fitter - Trade Theory

FITTER - CITS

LESSON 24 : Introduction and necessity of surface
finishing

Objectives

At the end of this lesson you shall be able to
• introduction to surface finishing process
• state the different types of surface finishing process
• state the advantages and uses of surface finishing
• state the difference between surface and waviness, examples.

Introduction:
When components are made either by machining or by hand, the movement of the cutting tool leaves some lines or
pits on the surface of the work. This is called surface texture. These are actually irregularities caused by the uniform
or uneven spacing of the production method. Due to which the shape of the pattern is formed on the work piece.
Types of Surface Finishing Process

Surface finishing processes encompass a variety of methods tailored to enhance the texture, appearance, and
performance of materials and components. These techniques fall into two main categories:
Electropolishing: This method removes ions from the surface, which is ideal for achieving smooth and flawless
finishes on metals like stainless steel, aluminium, and copper.
Painting: Techniques like spray painting and powder coating enhance aesthetics and corrosion resistance, widely
applied in automotive manufacturing.

Sanding or Sand Blasting: Manual surface finishing involving abrasion to remove imperfections from materials
like aluminium, carbon steel, and stainless steel.
Electroplating: Electroplating uses electric current to deposit metals from a solution, offering benefits like increased
durability and corrosion resistance for metals such as zinc, copper, and gold.
Vacuum Plating: Utilising high vacuum environments, this method includes processes like sputtering and ion
plating for precision applications like titanium nitride surface treatments.
Thermal Spraying: This process involves heating and accelerating materials to mechanically attach them to
surfaces, often used for structural elements and thermal barrier coatings.

Chemical Treatment: Chemical reactions create thin oxide or sulphide layers used for colouring, corrosion pre-
vention, and priming surfaces for paint applications.
Powder Coating: Electrostatically applied dry powder adheres to surfaces and is melted, offering durable finishes
for a wide range of items.
Hot Dipping: Components are dipped into molten solutions to create metallic coatings, primarily for corrosion
protection, as seen in applications like guardrails.
Advantages of Surface Finishing Process

The various advantages of Surface Finishing:
• Enhanced appearance.
• Improved corrosion resistance.
• Increased durability.

• Reduced friction.
• Better electrical conductivity.
• Tighter tolerances.
• Stress relief.

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