Watch Plating 101 Primer 01 02 03 04 05 06 07 08 09 10 11 12 13 14



factor 5 - Porosity: It would be easy to write a whole chapter on the many important technical relationships that can lead to porosity (i.e. transverse pores, bulk porosity) in goldplated finishes.

When electroplating begins forming the first layer of gold onto the watch case, the gold is gradually constructed at a molecular level in a "lattice type" layer structure. The longer the watch is exposed to the plating bath the thicker and denser the gold lattice layers will be.

If there is any contamination on the surface of the watch case or uneven roughness (i.e. scratches) in the finish, the molecular lattice structure of the gold can be interrupted and a microscopic "pore" can form and begin growing at the contact point. If this and other factors (i.e. plating baths, power supply) in the electroplating process are not tightly controlled, porosity resembling layers of microscopic swiss cheese will occur throughout the goldplated layer.

Unfortunately, porosity can allow the brass watch case to slowly corrode as surface contaminants migrate through the tiny pores in the gold layer. Eventually this corrosion will travel back to the surface of the goldplated finish of the watch and cause it to change color. This is one of many reasons why the gold finishes of replated watches have such a bad reputation for not lasting very long. Therefore, it is vital that all porosity be minimized or completely eliminated during the gold electroplating process.

There are a few ways to achieve this. First, you should keep in mind that there appears to be an important relationship between gold thickness and porosity formation. Simply stated, porosity decreases as the gold layer becomes thicker. As the goldlayer is built up, new layers of gold bridge over and "seal" any pores that were formed during the beginning stages of the electroplating process. Goldplating in sufficient thicknesses combined with proper electroplating processes can virtually eliminate any chance of surface contaminants from migrating into the brass watch case. This is why a heavier layer of goldplating should be utilized.

It is important that the plating process utilizes some type of protective underplating process. As mentioned earlier, bright nickel can be utilized as an underplating to prevent any contaminants from traveling to or from the brass watch case and eventually discoloring the goldplated layer.

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