Ever wonder why your metallic powder coating appears to shift after applying a clear coat?

We highlight this concept and offer some easy adjustments you, as a powder coater, can use to minimize issues when applying a clear coat to metallic powders.

The application of a clear top coat over a metallic finish is not always a requirement but it does create a more durable finish overall and in some cases it will protect the metallic flake from oxidation. However, there are some metallic powders, more typically silver or gold colors, which can suffer a shifting of the metallic after the clear has been applied and baked. This happens because the metallic is not stabilized in its flowed form. As the clear top coat melts it bonds with the metallic flake causing it to move as it flows out. Sometimes the change is hardly noticeable but other times it can be drastic in appearance. It's always a good idea to run samples beforehand so that you know how a clear will affect the base color (see these simple steps for better powder coating).

You can adjust how much the metallic will move based on how long you allow the base metallic coat to bake for. Instead of removing a coated item from the oven right after flow out, allow it to bake an additional 5-10 mins to allow the metallic flake to stabilize. How much extra time is necessary will depend ultimately on the powder itself and the substrate material type and thickness.

Always keep in mind, the longer you allow a base coat to cure before top coating, the less the top coat will be bonded to it (inter-coat adhesion) which decreases the overall durability of the top coat, leaving it more prone to chipping and in some cases delamination. Thus, it is not always the best coating procedure for the every application.

It is ultimately up to the powder coater and the end user (customer) to make an informed decision. Which is more important, aesthetics or durability? Just as it is for individual powders, not all application methods are well suited for every situation.

Make sure you work with a reputable coating shop who will take the time to help you understand the process limitations.

Please go to our applicator locator in order to help find a nearby powder coat applicator.