The reason metal needs to be treated is so it can adhere better to the coating that it receives. It also helps to prevent corrosion and wear over time. The process of chemical metal treatment happens in four steps and is done to clean the metal and prepare it for coating.
Step One: The Degreasing
The first step in the treatment process is de-greasing. This will remove the impurities from the surface of the metal and can be done is a few different ways. The solvent cleaning method uses a Benzene or Kerosene cleaning agent to wipe the metal. This is the cheapest method to use and is the best method available. The vapor degreasing method uses a different type of solvent which removes light oils but doesn't do much to the heavier oils. These are two are the most common methods for degreasing metals.
Step Two: De-Rusting
When something rusts it is because iron has oxidized. The de-rusting step is one that's required when working with steel and iron metals. This will prevent rust from forming when the metal gets wet. The de-rusting step uses an acid such as Sulfuric acid to remove any of the oxidation.
Step Three: Activation
Activation is the process that makes sure the coating step goes smoothly and is uniform. There are two types of activation. The first is the basic activation method which uses titanium based compounds to prepare the metal for the coating phase. The second is the acidic activation which uses an acid bath.
Step Four: The Coating Step
Some of the advantages a powder coating has is that they allow the company to have a solvent-free workplace, which makes cleaning a lot easier. If the powder coating is not uniform then the painting process will not go smoothly. You want an even layer of the coating so paint won't be defective on your final product.
The most common material used for coating is phosphate. It will give the metal a clean surface and helps prevent a bad reaction between the metal and the next step which will be the painting. There are two types of phosphate coating methods zinc and iron. Zinc is used on automobile and hardware metals. While iron used in treating a limited amount of metals, it is easier to apply than the zinc phosphate method. Phosphate coating can be used for cadmium, tin, zinc, aluminum, cast iron, low alloy, and carbon steel. There is also chromate coating which involves a reaction between chromium salts and the metal. It can be used for cadmium, zinc, magnesium, and aluminum.
Metal is treated in order to optimize both the physical and mechanic properties for the intended application. While the choice in powder coating or the cleaning method may vary from one treatment to the next, the process always involves this basic four step process.