You may ask yourself what are Dormant powder coatings?
Dormant powder coatings are a class of metallics where the dye or vibrant pigment is bonded to a metallic creating a basecoat then a clear topcoat is sprayed over the basecoat to create the final finish. During the cure, the dye travels from the bonded basecoat and settles within the clear coat itself. The ability for the dye to travel is because dyes are soluble by polymers, while pigments are relatively insoluble. Due to the nature of the dye, a unique optical effect occurs where the metallic looks distant compared to a regular bonded metallic. The reason that these are called dormant is that, sprayed without a clear topcoat, it looks like a regular metallic – it is only when the clear coat is applied that the overall effect takes place.
The most common clear topcoat used for dormant effect is a high gloss clear based on the attractiveness of the shiny metallic and overall aesthetic. Any clear can be used on a dormant and the same effect can be achieved. The variation that you’d see using a high gloss clear compared to a satin or matte clear is the same variation that you’d expect to see with the same product at two different gloss ranges. The light reflected off will not be as brilliant when you use a low gloss clear due to the way that low gloss clears are made, some cloudiness could be expected. At most, you’d achieve mainly a dull metallic appearance using a low gloss clear, rather than the high sparkle or reflective appearance with a high gloss clear.
It is important to refer to the proper Product Data Sheet for the correct curing parameters for Dormant powder coatings. It is advised that the base dormant is cured for 2.5 to 5 minutes at 200 C (substrate temperature) then a clear coat is applied and cured fully. The reason for this is to allow for better adhesion of the clear coat to the base dormant – the gel state that the dormant is in allows for the clear to “latch onto” the basecoat and adhesion between the two is improved significantly. It is important to make sure that the minimum curing for the dormant is completed, otherwise the flow of the dormant can be affected and a crackled or muddled appearance might occur. This is because the basecoat will still attempt to flow and settle while the clear coat is also trying to settle and flow. If we over cure the base dormant, then the clear may not apply correctly to the dormant and we could expect issues with intercoat adhesion.
To find more about Dormant powder coatings, please refer to our Series 49 PDS.