Surface Finishes and Treatments

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1 Surface Finishes and Treatments

  • There are a range of different surface finishes and treatments that can be applied to materials.
  • Some are applied to protect the material.
  • Some are applied for decoration..
  • Some are applied to do both.

Metal Plating

  • Metal plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years; it is also critical for modern technology.
  • Plating is used to decorate objects, for corrosion inhibition, to improve solderability, to harden, to improve wearability, to reduce friction, to improve paint adhesion, to alter conductivity, to improve IR reflectivity, for radiation shielding, and for other purposes. Jewelry typically uses plating to give a silver or gold finish.
  • Cheap metals can be coated with a more expensive one, such a gold to make it look more expensive.
  • Some metals corrode and can be coated to prevent or minimise this. For example, steel can be coated with chromium which provides excellent corrosion resistance.

Insulating Coatings

  • Electrical cable are needed to transport electrical current around. These need to be covered by an insulating material to prevent them from touching each other and to prevent electrocution.
  • PVC is a common electrical insulator and is used to coat electrical wire.
  • PVC can also be produced in many different colours, which is very useful for colour coding wires.
  • When using higher voltages and current, such as mains electricity, the cables are then double insulated with a flexible insulating case.

cables.jpg

Resistor Colour Codes

  • Resistor codes we have looked at previously is a way of using surface finishes.
  • We use the colours on the surface to create colour bands that are used to identify the value of the resistor.

Finishes applied to cases

  • Finishes are applied to the surface of a product to protect and decorate is.
  • Here are some common finishes:

finishing.jpg

2 Practise Questions

Practice Questions

  1. What materials can electroplating and anodising be used on?
  2. Why are copper electrical cables covered in PVC?
  3. Plastic is sometimes called self finishing. What do you think this means?
  4. What finish could you use for the following products? Say why.
    • A steel light fitting.
    • The plastic case of a cordless drill.
    • The alumininium case of an expensive smartphone.