There are many different methods of metal surface treatment. Metal surface treatment is a process where metal parts are prepared for painting. The preparation is commonly referred to as coatings pretreatment. This usually involves creating a physical barrier that will protect metal against a corrosive environment.
The surface films used in chemical conversion coatings are formed by a means of a non-electrolytic chemical reaction that occurs between the metal surface and solution. They are adherent, inorganic crystalline or amorphous films. For the metal surface treatment to form a protective film, the base metal needs to be converted to the one of the components that is less reactive to corrosion than the original metal surface.
To create the proper metal surface treatment, the film must impart equal potential to the surface and neutralize the possible anodic and cathodic corrosion areas (see Zinc Phosphate for more information). The metal surface treatment then provides an absorptive base for adhesion to finishes, like paints.
There are several steps included in the metal surface treatment process. The first step is cleaning where the mill oils and stamping compounds are removed. This is followed by a cleaner rinse and then onto a conversion coating stage of either iron or zinc phosphate. There is a rinse after the phosphate stage, which is normally followed by an inorganic-organic sealer. The final step is rinsing with pure water like de-ionized or reverse osmosis water. The parts then travel to a dry-off oven to remove all moisture before painting.
The most common type of metal surface treatment is chemical conversion coatings. Iron and zinc phosphate coatings are normally referred to as conversion coatings. Iron phosphates and zinc phosphates are formed using simple equipment and Vanchem products such as FOSTEX JSF and FOSTEX ZN.