Surface finishing Flashcards
What is painting used for?
Decorative and corrosion resistance coating for metal surfaces
Advantages of painting
Easiest and cheapest way
What does pigment do in paint?
Provides paint with colour
What does vehicle do to paint?
Part that has to form film where paint dires
and sticks to surface
What does solvent in paint do?
Controls how easy the paint is to apply
evaporates as paint sets
How can paint be applied by?
Brushing , spraying or dipping
What does plating uses?
Proces called electrolysis to coat surface of metal with thin layer of material
What does part need to be coated in plating?
Put in bath/tank containing solution of chemical salts and anode
What is anode in plating?
Piece of metal that will be used in coating
How is a thin layer formed in anode?
Electric current passed throug part , solution and anode
anode gradually dissolves away
How is chromium plating different from plating?
Anode doesn’t dissolve into chemical solution
extra salts have to be added
nickel plat to improve corrosion resistance
What is anodising?
Plating process which often used on aluminium
electrolysis in acid solution
Advantages of anodising process
- Durable
- corrision-resistant finish
- colour added for decorative purpose
What products made from anodising?
- Dielectric film
- anodised titanium used for dental implants
What does galvanising involve?
Dripping metal into bath of molten zinc
liquid zinc sticks to steel and cools to form coating
What material is typically used for galavanising?
Mild steel
Advantages of galvanising
Zinc provides good corrosion resistance
appearance of coated part isn;t attractive
What is galvanising used for?
Metal dustbins
buckets
road signs
What happens during etching?
Selected areas of surface are dissolved by chemical actions
Why is etching used in PCB?
Tracks needed for electricity to pass
How is etching also used
Decorative finishes on ceramic items e.g glass
What is polishing?
Physical process that gives surface a smoother , shiny appearence
