How is plating done on metal zippers with or without electrolysis? (i.e. with electricity or just with dipping process?)i have found out that for...

There are two techniques of plating metals and alloys: electroplating and electroless nickel plating.

Electroplating method is using electrical current and the process is called electrodeposition, where the cathod is the object to be plated and the anod is made fromthe metal to be plated on the object. Alloys like brass and solder can be electrodeposited.

The tough step in this process is the uniform thickness of the layer, especially if the object to be plated has a complex shape or is a very bad electrical conductive. Though, the complex geometry issue, can be solved by using more anods or a special  form anod which copies the geometry to be plated.

Electroless nickel plating is an auto-catalytic chemical method which is making possible to put a layer of nickel-phosphorous or nickel-boron alloy, on a solid object made of metal or plastic. Unlike the other plating technique, electroplating, this one can be used on complex shapes and non-conductive objects, because is not using electrical current.