Why it’s Used and How to Use it
While rust is an enemy of metal, causing corrosive effects that can devastate the metal and cause corrosion damages of approximately $276 billion a year in the United States. Zinc plating is used to protect different kinds of metal like iron and steel from corrosion. This involves electro deposition and a thin coating of zinc on the surface or substrate of the metal. Zinc coating creates a barrier preventing moisture and oxygen from reaching the metal underneath. It’s chosen for its ability to fight corrosion.
Humanity began using zinc compounds more than 2,500 years ago. Metallic zinc first occurred around the 15th century in India. Now the coating of a metal surface to protect it from rust, which is called galvanization, is the use of one-third of all zinc metal. Zinc plating, in fact, is the most frequently used method of galvanization.
Though zinc plating is very useful, it is a relatively new method. Not widespread until around 1980, cadmium was preferred by metal platers to protect from corrosion. It just so happens that cadmium is highly-toxic and poisonous after an extended period of interacting with it.
Zinc, on the other hand, is considered much more bio-friendly. Although its ability to prevent corrosion isn’t as large as cadmium, cadmium plating is usually restricted to areas that zinc won’t sufficiently protect from corrosion.
The Process of Zinc Plating
Zinc plating is a complex process requiring a lot of expertise and specialized equipment and machinery. The equipment needed includes a plating station, a rectifier, an ancillary tank for proper dissolution of the zinc anode, and a reservoir. Once you have all of these, you will be able to start the multi-step process.
First, you must prepare and clean the surface of the substrate. Contaminants or debris on the surface will prevent proper zinc coating, so you should clean it with an alkaline detergent solution for surface cleaning. Then, following the detergent, apply acid treatment to remove any rust, a process called pickling. Immerse the substrate in an electrolyte solution, such as acid or alkaline zinc, that is specifically formulated and called a plating bath. Consisting of a zinc ion solution and other chemicals, the bath helps produce the desired physical properties.
After cleaning and preparing, it is time to apply a specific plating procedure. You either want to use rack plating, which is when larger parts are affixed to metal racks that are placed inside a tank for a plating bath or barrel plating. This is normally used for smaller parts that are placed inside a barrel and rotated inside of a tank. This leads to a finish that is more thorough and uniform.
When you have decided what kind of plating you will use, next comes electrodeposition. An electrical current is used to deposit metal ions onto the surface of the metal substrate. The DC current is introduced to the bath, zinc is deposited onto the surface, and the current flows back to the anode to complete the circuit.
Finally, post-treatment involves rinsing parts in water to remove contaminants and anything left from the plating bath. Rinse several times if you still have contamination. The last step is to dry the zinc plates thoroughly. If you need additional protection from corrosion, passivators and sealers can also be included in post-treatment.
To find out more about zinc plating, contact our specialists. Kramer Industries will help you finish off your project right.