Powder Coating Process Adhesion
The charged powder particles adhere to the electrically grounded surfaces until heated and fused into a smooth coating in a curing oven. For thermoplastic systems once the powder flows out and cools the coating process is complete.
Adhesion problem of powder coating application poor adhesion is usually related to poor pretreatment or under cure.
Powder coating process adhesion. I have recently had an issue with powder coating adhesion to aluminum processed through my single stage pretreatment system. As with the cure test your adhesion test results can be affected by overbake or underbake generally adhesion testing kits are available for specific testing requirements. There are many things in powder coatings that can affect adhesive bonding.
These are subjective and somewhat inconclusive. Glossy colors the more difficult it is for adhesives to bond. Adhesion of coatings is a complex phenomenon depending on surface energy chemical bonds surface roughness cleanness and mechanical strength.
Duplex coating involves sweet abrasive blasting over the substrate pretreatment zinc primer base coating and top coat. Powder coating adhesion testing. After performing energy dispersive spectroscopy testing on the failed areas it was determined that a layer of magnesium was on the surface of the aluminum which became brittle after powder coating and separated so that the coating released from the substrate.
Zinc coated metal can be galvanized or hot dip galvanized. This coating can be re melted with the application of heat. The second problem is compatibility.
Undercure run an electronic temperature recording device with a probe on the part to ensure that the metal temperature reaches the prescribed cure index time at temperature. Powder coating adhesion testing adhesion testing measures how well the powder sticks to the part once it is fully cured. First is surface smoothness.
Galvanized metal is very easy to prepare for powder coating a duplex coating can ensure proper adhesion and preparation for powder coating. Therefore excellent adhesion should be expected from functionalized roughened cleaned and cross linked polymer surfaces enabling covalent bonding of the coating. In many high end applications the part is electrocoated following the pretreatment process and subsequent to the powder coating application.
The powder used for the process is a mixture of finely ground particles of pigment and resin which is sprayed onto a surface to be coated. Sir is there a more accurate test method for adhesion of powder coat than cross hatch and pencil hardness. For both types a free flowing dry powder is applied to a substrate usually metal which is then heated to a temperature that allows the powder to melt flow and form a coating.
This has been particularly useful in automotive and other applications requiring high end. The result is a uniform durable high quality and attractive finish. A discussion started in 2000 but continuing through 2019.
Titanium zirconium and silanes offer similar performance against corrosion and adhesion of the powder. The smoother the surface i e.