Powder coating is a dry finishing process that uses an electrical charge to cause a dry powder to fuse to the metal’s surface. Powder coating is actually preferable for most purposes, even though painting is quicker and more cost-effective. Powder coating is primarily used to coat metals like household appliances, aluminum extrusions, drum hardware, automobiles, and bicycle frames.
Why is Pretreatment Important?
The pre-treatment is the process of chemical preparation of various types of metal and aluminum prior to the application of a powder-coated finish. A well-prepared metal surface is required for a perfect powder coating. Pretreatment is a prerequisite for powder coating any metallic surface. The pretreatment is done for three purposes:
- Provide temporary in-process corrosion protection before the application of powder coating
- Encourage good powder coating adhesion to the substrate.
- Impart under paint corrosion and thereby improve the life of powder coating.
Pretreatment for powder coating cleans and seals products prior to powder application.
Pretreatment is an effective method of removing oils, greases, and other impurities. In many cases, pretreatment reduces the need to add abrasive blasting, thus saving money. Pretreatment seals products at various stages of the process for added protection and improved adhesion between the metal surface and the primer.
The pre-treatment procedure is also known as the “Seven Tank Powder Coating Process.” The pre-treatment is a crucial process for ensuring long-lasting results. The 7 tank process for powder coating is listed below.
What are the Pretreatment Steps?
1) Degreasing is the first stage in which oil, grease, and dirt are removed from the metal surface. Alkaline degreasers are a blend of alkalies and surfactants, commonly used for the purpose
2) Rinsing is the next action. The purpose of a water wash is to remove the degreasing effect on a metal surface. It removes chemicals while going to the next level
3) The third step is derusting, which involves submerging the product in chemical solutions to remove rust, scale, and an oxide layer from the surface.
4) As the fourth procedure, rinsing Is once more repeated. The effects of the de-rusting chemicals on the metal surface are eliminated by the water wash which stops the derusting Chemicals proceed further, as they are acidic in nature.
5) Surface activation comes in fifth. This stage is optional, during phosphate coating surface activation agents activate the metal to obtain a fine crystalline structure. This will increase corrosion resistance and adhesion properties.
6) The sixth and most significant process is phosphating. The coating of sheet metal is made smooth and homogeneous by employing a phosphate solution and chemicals. Zinc Phosphate coating is grey in nature. A Series of phosphate coating gives the best results.
7) The last phase is passivation. A chrome layer is formed over the zinc phosphate during passivation. This increases the corrosion resistance protection of the metal parts. It seals the pores of sheet metal surfaces for obtaining maximum corrosion resistance over phosphate coating.
So pretreatment is a must for powder coating for bringing long-lasting effects and adding value to your application.
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