3: Wood & Metal Finishes

Question 1

Paints

Answer 1

[Metal & Wood]

Question 2

Varnishes (1)

Answer 2

[Wood]
1. apply thin coat in direction of grain

Question 3

Sealants (3)

Answer 3

[Metal]
1. applied with cloth or machine pad
2. produces a film that is cured
3. then it is buffed to a shine

Question 4

Preservatives (3)

Answer 4

[Metal]
Applied by:
1. wiping with cloth
2. spraying
3. immersion of the product

Question 5

Anodising (2)

Answer 5

[Aluminium]
1. electric current passes through sulphuric acid electrolyte from part to be treated (+ve anode) to a -ve cathode
2. an aluminium oxide layer builds up on the treated part

Question 6

Electroplating (2)

Answer 6

[Metal]
1. electric current passes through sulphuric acid electrolyte from part to be treated (-ve cathode) to a +ve anode (donor metal)
2. treated part attracts donor metal & is coated in the donor metal

Question 7

Powder Coating (4)

Answer 7

[Metal]
1. product is negatively charged
2. polymer powder (+ve charged) is sprayed (airgun) and attracted to product
3. product is baked in an oven
4. heat melts the powder to form even coating

Question 8

Oil Coating (3)

Answer 8

[Wood]
1. rub oil onto wood (grain direction) with a lint-free cloth
2. let wood absorb oil & rub away excess
3. lightly sand to open grain between coats

Question 9

Galvanising (2)

Answer 9

[Metal]
1. metal part is cleaned (in flux) & degreased
2. metal is coated in molten zinc at 460°C

Question 10

Cathodic Protection (5)

Answer 10

[Metal]
1. The sacrificial anode is attached to the metal needing protection.
2. The anode shares electrons with the protected metal.
3. When exposed to a corrosive environment, an electrochemical reaction begins.
4. The anode rusts (corrodes) and releases electrons.
5. The protected metal receives these electrons, preventing it from rusting