Q: We do auto restoration and are asked to provide high-shine, chrome-like powder for parts like intake manifolds, wheels, etc. What is the brand and number of the brightest powder that you are aware of?
We have been using a commercial product with a clear coat (the clear protects the base from oxidation), but the clear knocks the shine down significantly. Are there any techniques on applying clear that would help?
A: Finding a chrome-look seems to be the Holy Grail in powder coating technology. All of us powder coating formulators have the same aluminum flakes available to create a shiny chrome-like (not chrome-look) powder. We use leafing aluminums to provide the patina-like sheen, but we have never approached the brightness of a plated surface.
Using a clearcoat, however, should enhance the brightness – not diminish it. It’s important to marry the clearcoat with the silver metallic basecoat. Using the same chemistry is a good start. It’s also wise to fully cure the basecoat before applying the clearcoat. Any movement or emission of volatiles from the basecoat due to undercure will reduce the clarity and brightness of the clearcoat.
It’s also vital to provide the highest smoothness of the basecoat; otherwise, the clearcoat will mirror the texture of the basecoat. Getting a smooth basecoat means (1) using a smooth powder to begin with, (2) applying the recommended thickness (too thin will create texture), and (3) laying down an even coat; avoid electrostatic “pop-off” with moderate gun voltage and distance to the part.
The same care taken with applying the basecoat applies to laying down the clear topcoat. One very important issue is to ensure that you have a very good ground (earth) to the part you are coating. This is especially important when applying a powder to an already-coated part. Poor grounding will result in uneven and thin deposition of powder. It is wise to reduce the current and kVs so you don’t build up too much charge on the part surface. Too much charge causes back-ionization and the physical “pop-off” of powder. This reduces the smoothness and brightness of the finish.
As for recommending a supplier of the brightest chrome-like finish, I think most powder suppliers have comparable technology. There is a technology recently pioneered that provides a chrome-like finish using powder coating. At least three companies use it. It consists of a multi-layer process, beginning with a very smooth powder basecoat that is cured completely. The coated part is then introduced into a vacuum metallizing chamber, which deposits an extremely thin layer of metal (typically aluminum).
This aluminum layer is incredibly bright but will oxidize and lose brightness within minutes. Consequently, the next step is the application of a very smooth powder clearcoat (typically an automotive-grade acrylic). This creates the closest approximation to a chrome finish using a powder.