Why surface preparation is critical to the desired function of powder coating
In order to obtain the desired functional and mechanical characteristics through powder coating Toronto, it is important to select the proper surface preparation method. The best option should prepare the part to ensure that the best adhesion is possible. In fact, 75% of all coating failures are due to incomplete or improper surface preparation. Metal surfaces usually have small pieces of dirt, grime and grease that have to be removed otherwise they can interfere with the ability of coating to adhere to the surface. However, mill scale and rust cannot be removed by water and detergent and requires abrasive blasting with water or compressed air to direct a high velocity of abrasive materials on the surface prior to the application of powder coating. It is suggested to use water in delivering the abrasives to minimize dust that is hazardous to the health of workers.
Phosphating to improve powder coating adhesion
Phsophating is usually referred to as conversion coating because the process involves metal removal as part of the reaction. Phosphate crystals act as organic coatings and corrosion barrier. When phosphate is present under the powder coating layer, rust creep is reduced. In some applications, phosphate is used as a standalone coating for purposes of lubricity in parts forming. Typical phosphating chemistries used are iron phosphate, zinc phosphate and manganese phosphate. Some chemistries have also been developed to work well in room temperature. The improvement of phosphate process has been the thrust in the development of different chemistries to reduce the temperature requirements of the phosphate bath.
Curing process for powder coating
Powder coating is applied electro-statistically after which the part has to be cured at elevated temperatures. Drying and curing are the energy intensive parts of the process of powder coating Toronto because of the need for convection ovens. However, convection ovens when used for large and heavy powder coated parts can be rather slow and costly because curing is largely dependent on the bulk temperature of the part. It is important for the part to be hot enough to cause the part surface to dry and for the powder coating to cure. Large volumes of air must be heated at the right temperature and exhausted from the convection oven for faster curing time.
Curing time is highly dependent upon part geometry. Simple geometries can be dried and cured through infrared heating. Infrared light heats the part surface and not the paint so that it dries from the inside out. Rapid part surface heating results into better powder flow with less potential for dust and dirt particles to settle on the surface.