Q: What is considered world-class first-pass yield in a powder coat system? Our system consists of two alkaline cleaners, zirconium conversion coating, high edge film build epoxy e-coat, followed by TGIC powder topcoat.
A: First-pass transfer efficiency is affected by several factors. Part geometry and how the parts are presented to the application system have a significant impact on deposition performance. In addition, primers reduce the transfer of charge from the powder to earth. Consequently, some factors require close attention and optimization.
Establishing a rock-solid ground is paramount, as is hanging and spacing parts in an optimal arrangement. Furthermore, manual vs. automatic spray will influence transfer efficiency. A good manual sprayer can outperform a so-so automated system.
All that said, I would expect a first-pass transfer efficiency of around 55-65% for a well-designed system spraying three-dimensional parts. It would be much lower for something like wire racks (spraying more air than parts) and somewhat higher for simple two-dimensional parts such as door panels.
In your case, the gun settings should be optimized with lower current to offset the insulative effect of the primer. Your application system supplier can give you more precise settings for their equipment.