2.9 Finishing - Metals

Question 1

What is sandblasting (bead blasting)?

Answer 1

• A finishing process for smoothing, shaping and cleaning a hard surface by forcing solid particles acroos that surface at high speeds
• The effect is similar to that of using sandpaper, but provides a more even finish with no problems at corners or uneven surfaces

Question 2

What does sandblasting equipment consist of?

Answer 2

• A chamber to which sand and air are mixed
• The mixture travels through a hand-held nozzle to direct the partocles toward the surface.
• Nozzles come in a variety of shapes, sizes, and materials

Question 3

What is anodizing?

Answer 3

An electrochemical process which converts Aluminum into aluminium oxide on the surface of a component

Question 4

Why is anodizing useful?

Answer 4

Anodized aluminium has increased corrosion and wear resistance, and provides better adhesion for paint primers and glues than bare aluminium.

Question 5

Why is anodizing not useful for Iron or Carbon steel?

Answer 5

Because the surfaces will be converted into Iron Oxide (rust) which will flake off and expose the ferrous metals to more rusting

Question 6

Why is the process called Anodizing?

Answer 6

Because the part to be treated forms the anode electrode of an electrical circuit

Question 7

What is the process of anodizing?

Answer 7

1. A cathode is connected to the negative terminal of a voltage source and placed in the sulphuric acid solution
2. an aluminium component is connected to the positive terminal of the voltage source and also place in the solution
3. when the circuit is completed, the oxygen in the solution will separate from the water molecules and combine with the aluminum to create the anodized coating.

Question 8

What is dip coating?

Answer 8

The process of dipping metal into a tank containing coating plastic material, removing the piece from the tank and allowing it to drain. The coated piece can then be dried by force-drying or baking

Question 9

What are the stages of dip coating?

Answer 9

1) Immersion - the meta is dipped in the plastic coating material solution at a constant speed
2) Dwell time - the metal remains fully immersed and motionless to allow for the plastic coating to apply itself to the metal
3) Withdrawal - the metal is withdrawn, again at a constant speed.
The faster the metal is withdrawn from the tank the thicker the plastic coating material will be.

Question 10

What is enamelling?

Answer 10

A finishing process that fuses coloured powdered glass onto metal by firing in a kiln, usually between 750 and 850 degrees Celsius

Question 11

What does the powder melt, flow and then hardens to?

Answer 11

A smooth, durable on metal, as well as Glass or Ceramics

Question 12

Why would you enamel mild steel and copper?

Answer 12

To add colour and prevent corrosion

Question 13

What is enamel paint?

Answer 13

A hard surfaced paint that is made from oil-modified polymers and air dries to a very hard glossy finish.

Question 14

Which enamel paints have been made by adding varnish to oil-based paint?

Answer 14

Latex and water-based paints

Question 15

Where is enamel paint used?

Answer 15

Available as high gloss finish for protecting flooring and Cast Iron railings and gates.