Additives are an important component when formulating powder coatings—and they can also create their own challenges when developing a coating that provides a coarse, stable, reproducible structure, a hammertone or an antique finish.
Cellulose acetate butyrate (CAB) is one of those additives that is commonly used in powder coatings to produce a coarse structure. However, due to the very low dosage levels of CAB that must be used in formulations plus batch and grain size fluctuations, the risks of errors when weighing CAB or uneven distribution are fairly significant. Either one will ultimately lead to inconsistent properties in the finished powder coating.
To overcome these potential challenges, powder coating additives must enable better dosing and homogenization, which leads to a more consistent and reproducible formation of a coarse structure in the final coating. Additives should also result in a robust structure even with double extrusion.
In the formulations of roughly structured, hammertone or antique-finish powder coatings, special additives are used which lead to the desired rough structure via different surface tensions and incompatibilities.
To coat a control cabinet with powder coating, a roughly structured powder coating is typically used. Scratches in the sheet metal due to processing, impurities, welding spots and other minor defects in and on the surface can be concealed by the coating using a roughly structured powder coating. The structure of mountains and valleys and the different refraction of light on the powder coating surface mask any visible defects.
A hammertone coating works well for applications that need an extremely robust coating and have to stand up to being hit, scratched or dropped, like machine housing or garden fencing. The right formulation will deliver an extremely scratch and impact-resistant powder coating that also covers surface defects.
To give metal furniture, lamps, mailboxes or other items a noble, antique look, an antique finish powder coating is used. These coarsely structured coatings with different metallic effect pigments produce an elegant, noble appearance that can conceal substrate problems of the object at the same time through their play of colors with glittering metal.
It’s important to work with an additive supplier who can help overcome any challenges when developing a variety of finishes that can provide difficulties when formulating. Lubrizol has a fully equipped powder coating laboratory and understands the challenges and trends of the market after many years of working closely with powder coating formulators.
Contact us to learn more about our powder coating additive capabilities.