1.5 Metal Finishing Flashcards

1
Q

What is the simmilarity between copper and stainless steel when it comes to oxidising

A

A oxide layer over the copper and stainless steel forms and protects the copper and stainless steel from corrosion

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2
Q

What is the difference between rusting and passivation and give an example metal for both

A

Rusting:
Iron/Steel - A slow and continuous rate of oxidation with an oxide layer that continues to crumble and flake away.
Passivation:
Aluminium - An initially rapid oxidation produces an oxide layer which helps to prevent further oxidation.

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3
Q

What metal finishing does “Low cost but slow so only suitable for one-offs & small batches. Smooth or textured (hammered) effect” apply to

A

Brush painting

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3
Q

What metal finishing does “Basic equipment so suitable for one-off & batch production. Generally acrylic based nowadays. Matt, satin and gloss effects” apply to

A

Spray painting

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3
Q

Outline two ways that painting an iron railing will change its characteristics.

A

Providing a colour change and providing protection from corrosion

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4
Q

What are the 3 prep stages and 1 application stage for brush painting

A

Remove any loose rust, Stabilise rust with a chemical treatment, Clean & degrease

Apply the paint in 1-2 coats

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5
Q

Explain why a primer coat is required if a metal part is to be spray painted.

A

It creates a smooth even surface to stick to the top coat

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5
Q

Outline two ways that spraying a wheel will change its characteristics.

A

Change colour, Corrosion barrier

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6
Q

What are the 3 application steps of spray painting

A

Primer, Undercoat, Topcoat

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7
Q

What metal finishing does “Basic equipment so suitable for one-off & batch production. Limited control over the variables that affect output quality. Adhered layer up to 1mm thick.” apply to

A

Polymer powder dip coatiwng

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7
Q

What metal finishing does “Expensive and time consuming but suitable for batch production. Chemically bonded non-metallic layer. Hazardous chemicals” apply to

A

Electroplating

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7
Q

Outline two or more ways that chrome (chromium) plating a metal part will change its characteristics.

A

Provide water protection
To give a more shiny finish

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8
Q

Give examples of electroplated parts

A

Teapot, Kitchen taps, wall heater

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9
Q

Outline two ways that polymer dip coating a steel part will change its characteristics.

A

Provide a colour finish(Limited finish)
Provide a therm and electrically insulating layer
Provide a protective plastic layer

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10
Q

What are the 4 steps in polymer powder dip coating

A

Part is heated to 250oC in Thermoplastic powder e.g. PE is fluidised (air is forced through it)
The part is moved around to help ensure an even coverage is achieved
Heat from the part melts polymer onto its surface
A plastic layer forms over the metal, A smooth, continuous coating is achieved

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10
Q

Give examples of polymer dip coated parts:

A

Wire hangers, outdoor equipment frames

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11
Q

Outline one way that zinc plating a steel part will change its characteristics.

A

Provide a corrosion barrier

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11
Q

What metal finishing does “Cost effective for batch production. Chemically bonded layer. Highly functional finish.” apply to

A

Hot metal plating (Galvanising(With zinc))

12
Q

Give examples of galvanised steel parts:

A

Hinges, clamps, railings

13
Q

What metal finishing does “Upfront costs but suitable for batch production. Less wastage and more durable than a spray painted finish but less colour choices achievable” apply to

A

Polymer powder spray coating

14
Q

Outline two ways that electrostatically powder spray coating a steel part will change its characteristics.

A

Provide a protective plastic layer
Provide a colour layer

15
Q

Give examples of electrostatically powder spray coated parts

A

Dishwasher bodies, fridge bodies

16
Q

What part (The nozzle or the product) is grounded to earth and with what charge in polymer powder spray coating

A

Product is grounded at -ve

17
Q

What is the process of polymer powder spray coating

A

The electrode nozzle sprays the grounded product with a thermoset powder and the powder coated part is then placed into an oven to melt the plastic particles over the part and leave a even finish

18
Q

What are the 3 metal clear finishes

A

Varnishes/lacquers, Sealants, Preservatives

18
Q

What metal finishing process does “Low cost solutions suitable for one-offs. A degree of protection is achieved. Generally sprayed application but can be brushed or wiped on” apply to

A

Clear finishes

19
Q

What clear metal finish provides A clear protective finish.

A

Varnishes/lacquers

20
Q

What clear metal finish provides Chemical resistance, water-beading action (hydrophobic) and added shine.

A

Sealants

21
Q

What clear metal finish Helps prevent fingerprints, corrosion and condensation on surfaces. Can also help reduce friction on moving parts/surfaces.

A

Preservatives

22
Q

What metal finish does “Low cost solutions suitable for one-offs. A degree of protection is achieved. Generally sprayed application but can be brushed or wiped on” apply to

A

clear finishes

23
Q

What metal finish does “Expensive and time consuming but suitable for batch production. Chemically bonded metallic layer. Hazardous chemical” apply to

A

Anodising

24
Q

Outline two ways that anodising an aluminium part will change its characteristics.

A

Increasing hardness and toughness
Providing a colour to the part

25
Q

What are the 4 steps for anodising

A

Treated part
Porous oxide layer
Added dye
Sealed with lacquer

25
Q

Give examples of anodised parts:

A

Hard Drive cover, mobile phone cases

26
Q

Explain how an electrochemical cell is created.

A

When 2 metals join a current flows through them,when there is water added between the 2 a cell is made

27
Q

What corrodes in sacrificial annodes

A

The anode (more active metal) will be corroded and protect the cathode (less active metal).

28
Q

What are the 2 types of cathodic protection

A

Sacrificial annodes, impressed current

29
Q

Explain what happens when an electrochemical cell has been created.

A

The more reactive metal starts to corrode as current flows from the anode to the cathode via the water, then the cathode is more protected

30
Q

What metals are used for sacrificial annodes

A

More reactive metals such as zinc and aluminium are used as sacrificial anodes.

31
Q

Fill in the blank “The sacrificial anodes don’t have to _________ _____ the cathode to protect it, but will need to be _________ and ______ when they can no longer provide sufficient protection to the cathode.”

A

completely cover, monitored and replace

32
Q

What is the idea of impressed current

A

An underwater/ground pipe or structure (Cathode) is protected by a positive current flow and if any corrosion does occur it is at the Anode

33
Q

Why are steel food cans e.g. baked beans, now lined on the insides with more than just tin?

A

To prevent the food from corroding the can

34
Q

Give two reasons why cellulose paint is now not widely used.

A

As it is very harmful to human health
Emits a lot of odor

35
Q

How is pearlescent paint different to metallic paint?

A

The particles are ceramic rather than metallic