Practical Aspects of Metal Deposition

It is interesting to consider the metal deposition process from a microscopic point of view. A rate of 20 mA cm , corresponds to the deposition ofabout 50 atomic layers of metal atoms per cm s- This may be too fast for the adatoms to reach their equilibrium positions. It is indeed observed that the alloys formed during electrodeposition are not necessarily those corresponding to the phase diagram of the alloys involved at room temperature. 

The interaction between the substrate and the metal being deposited can also play an important role in determining the quality of a plated product. When the crystal parameters of the two metals are different, one of two situations may be observed. 

The effect is similar to the formation of small crystals in a supersaturated solution or of droplets in the vapor phase  

Side reactions, mostly hydrogen evolution, play an important role in electroplating. 

As a rule, their effect is detrimental to the process because of the loss of energy and possible hydrogen embritdement. 

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