Metal

Question 1

Different finishing methods for metal

Answer 1

Paint
Sealant
Preservatives
Anodising
Electroplating
Powder coating
Galvanisation
Cathodic protection

Question 2

Advantages of paint

Answer 2

Range of colours and textured
Used on low cost metals
Provides barrier against corrosion and decay

Question 3

Application of paint

Answer 3

Surface of metal cleaned and degreased to ensure grip for primer coat
Paint can be applied by either spray or a brush

Question 4

Disadvantages of paint

Answer 4

Undercoats often needed
And degreasing often ties time
Paint can chip

Question 5

Advantages of sealants

Answer 5

Protects surface from decay and tarnishing
Acts as a barrier
Increases toughness of surface

Question 6

Application of sealants

Answer 6

Applied with a cloth or machine and to produce a film that is cured for up to 15 minutes
Buffed with a cloth to shine

Question 7

Disadvantages of sealants

Answer 7

Mostly used as an extra on top of something else like a paint

Question 8

Advantages of preservatives

Answer 8

Create a smooth surface
Prevent fingerprints on moulds
Prevent minor corrosion and condensation build up
Medium to long term protection

Question 9

Application of preservatives

Answer 9

Wiping with a cloth, spray or immersion

Question 10

What metal is anodising used on?

Answer 10

Aluminium

Question 11

Purpose of anodising

Answer 11

Enhance the natural oxide layer resulting in increased hardness and toughness.
Add colour to product

Question 12

Uses of anodising

Answer 12

Torch casings
Casings for mobile phones

Question 13

Process of anodising

Answer 13

1. Electric current passes through sulfuric acid electrolyte solution
2. As current goes from anode (part to be treated) to cathode the oxide layer builds up producing the anodised finish
3. Further finishing can be used like a clear lacquer or a varnish to seal the finish and further protect it against scratches

Question 14

Disadvantages of anodising

Answer 14

Specific to aluminium
Specialist equipment needed (electrolyte solution

Question 15

Purpose of electro-plating

Answer 15

Provide a protective layer and to give a greater aesthetic appeal

Question 16

Uses for electroplating

Answer 16

Metal teapots are silver plated to provide increased aesthetic appeal as well as a barrier to corrosion from contained liquid
Kitchen taps are chromium plated to provide protection against the water and to give a shiny hardwearing finish

Question 17

Common metals used in electroplating

Answer 17

Silver
Gold
Zinc
Copper
Tin

Question 18

Process of electroplating

Answer 18

Similar to anodising
Product and donor material placed in electrolyte solution
Current applied across
Product attracts donor material and is electroplated

Question 19

Advantages of electroplating

Answer 19

Makes surface more hardwearing
Adds colour
Used on low cost metals

Question 20

Purpose of powder coating

Answer 20

Hardwearing finish

Question 21

Uses of powder coating

Answer 21

Washing machines
Dishwashers
Refrigerators
Fencing
Gates and railings

Question 22

Process of powder coating

Answer 22

Product is negatively charged
Thermoset polymer resin (positively charged) sprayed with air gun
Product attracts resin
Product baked in an oven to melt the powder resulting in an even coating

Question 23

Disadvantages of powder coating

Answer 23

Oven has to be correct size to fit product in

Question 24

Benefits of powder coating

Answer 24

More hardwearing than paint
Provides colour
Good for low cost metals like mild steel
Simple process

Question 25

Purpose of galvanisation

Answer 25

Uses zinc in order to protect other metals from corrosion and rust

Question 26

Process of galvanisation

Answer 26

Zinc is heated to temperature of roughly 460 degrees Celsius Product to be coated is then immersed in tank

Question 27

Disadvantages of galvanisation

Answer 27

Metal must be cleaned and degreased prior to dipping Dipping bath required

Question 28

Purpose of Cathodic protection

Answer 28

Protect steel structures buried in soil or immersed in water like ship hulls, pipelines or offshore platforms. Controls rate of corrosion by making the metal the cathode of an electrochemical cell. The anode is sacrificial

Question 29

Process of Cathodic protection (impressed current):

Answer 29

Part to be protected is connected to power supply (anode) Current flows from inert electrode (cathode) through liquid to the component to be protected The cathode corrodes over time and is monitored so the part is protected

Question 30

Process of Cathodic protection (sacrificial anode):

Answer 30

A sacrificial metal protects desired metal A more electrochemically active metal is wrapped around or joined to the less active metal to provide resistance to corrosion. This is then monitored and replaced when corroded through

Question 31

Advantages of Cathodic protection

Answer 31

Usage for underground/underwater products

Question 32

Disadvanatages of Cathodic protection

Answer 32

Products require frequent monitoring