Electroplating

Galvanic cells and batteries use chemistry to produce electricity, but the opposite is also possible. We can use electricity to drive chemistry. This process is called electrolysis and one of the reasons we do it is to plate one metal on to another.

Imagine that you had a well crafted spoon made of tin. No matter how good the workmanship, a tin spoon will never be pretty, since tin is a rather drab gray metal. So, how can we make the spoon more attractive? We could plate it with gold. 

To do this, we’ll need to set up an electrolytic cell, like this:

The container is filled with a solution of gold III nitrate. We are only showing the \(Au^{+3}\) ions and not the nitrate, since only the gold ions will be involved in the chemistry. On the right side is a gold wire connected to the positive end of a power source. As electrons are pulled away from the wire, some of the gold atoms become ions and move into the solution:

\(Au \rightarrow Au^{+3} + 3~e^{-1}\)

The left side has our spoon connected to the negative end of the power source. As electrons move into the spoon, the \(Au^{+3}\) ions are attracted to the spoon, take electrons and become neutral gold atoms:

\(Au^{+3} + 3~e^{-1} \rightarrow Au \)

These atoms join the spoon and create a layer of gold (only a few atoms thick) on the surface. As a result, our spoon will appear to be gold (since you can only see the atoms on the surface) even though it is mostly tin.