Zinc plating is done for a number of reasons, often for practical surfacing and sometimes for decorative purposes. Many times, things such as screws and car parts are plated with zinc during repair or to keep them in better shape, because this plating lasts so much longer than other surfaces and resists damage and corrosion. You can have this done at a shop, but you can also do it yourself at home.
The Setup: The part of the item that you will be plating has to be cleaned thoroughly before the process begins. To do this, soak it for 15 minutes in an alkaline solution first, followed by soaking for 15 minutes in a mild acid. You need a stainless steel or plastic container that is suitable for the amount of material you'll be using. You also need an electricity source and a current meter. You can get the zinc from ironmongers and scrapyards. You will find ammonium chloride, zinc chloride and electrolyte at pharmacies or chemists. You can also purchase all of these items in zinc plating kits instead of having to travel to so many places. This kit will include a power source, usually in the form of a 9-volt battery. The electric current runs from the positive battery terminal to the item being coated, which is submerged in an electrolytic solution. The current the travels from the plated item to the negative battery post, completing the electrical circuit. The current meter can be clipped into the electric current at any point to read how much current is passing through the connection. This will allow you to know when the battery needs to be replaced.
Methods: There are a few of different methods commonly used for zinc plating. One is hot-dip galvanization, which includes dipping the part into a container of molten zinc. This zinc has to have a layer of flux floating on the top of it. This flux is usually a solution of zinc ammonium chloride. This way the part will be covered in flux before the zinc. Once it is dipped, set it to dry. The other method is dry galvanization. This is similar, but the part is coated in flux and then left to sit and dry before being coated with the molten zinc. Both of these methods will result in the dry part being coated with something called "spangle," which is crystalline in appearance. You can control this by changing the drying time. There is also another method called cold zinc plating, which is easier but not as durable. It simply involves coating the part with zinc paint.
Drying: As the zinc dries, it will form a bond with the steel so that there is actually a transition point between the two materials. This means that the zinc cannot be peeled off. It is integrated right into the part. After a couple of days, the zinc with change into zinc oxide, which is good because it gives extra protection, about twice as much, to the part. After even more time, this will change into zinc carbonate, which adds even more protection, so the part will stay in good shape for a long time.
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