Compare and contrast galvanising and electroplating. Why might an engineering part beelectroplated rather than galvanised?

Galvanising and electroplating are both methods used to coat a metal object with another metal in order to provide protection against corrosion. However, they differ in their processes, applications, and the types of metals that can be used.

1. Process:

   • Galvanising involves dipping a metal part into a molten bath of zinc. The zinc reacts with the metal to form a protective layer that is actually part of the metal object itself.
   • Electroplating involves using an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. The part to be coated acts as the cathode of an electrolytic cell and the metal to be deposited on the part is used as the anode.

2. Applications:

   • Galvanising is typically used for larger parts and for applications where a thicker coating is required. It is commonly used in industrial applications for parts that are exposed to harsh conditions.
   • Electroplating is typically used for smaller parts and for applications where a thinner, more controlled coating is required. It is commonly used in electronics, jewellery, and automotive parts.

3. Types of Metals:

   • Galvanising is limited to using zinc.
   • Electroplating can use a wider variety of metals including gold, silver, nickel, and copper.

An engineering part might be electroplated rather than galvanised for several reasons. Electroplating provides a smoother, more aesthetically pleasing finish which is often required for consumer-facing products. It also allows for a greater choice of metals to be used for the coating, which can be selected to provide specific properties such as improved electrical conductivity or resistance to particular types of corrosion. Finally, electroplating allows for more control over the thickness of the coating, which can be important for parts with tight dimensional tolerances.