I am trying to find more information on fluidized beds for powder coating. What is their maximum size? What kinds of pre-heaters are used? Is it possible to apply a powder coating to hot-dip galvanized products right after galvanizing? The parts would be 750-800°F. J.N.
Fluidized beds can be made to accommodate just about any size part. Except for the fluidized beds that are used to support powder spray feed systems (called hoppers), each fluidized bed is custom designed for a specific end-use. That’s the good news. The bad news is there are few companies still making fluidized beds for powder coating in the United States. This market is very small compared to other mainstream powder applications and this resulted in many companies getting out of the business of making them. However, there are still some companies out there. Check with PF Online as a start (www.pfonline.com/suppliers.html).
Parts are preheated to 500°F or higher, to ensure that the powder coating is attracted to the surface and builds to the desired film thickness. Preheating can be accomplished by many means—convection, IR, near IR or induction—depending upon the part configuration and the desired heat up time.
I would doubt that a part can be fluidized powder coated immediately after hot-dipped galvanizing, since the gasses released during the cooling of the zinc will cause holes in the powder coating. Having a porous powder coating film on the part will reduce the mechanical and corrosion resistant properties of the coating, leading to poor performance in the field. Furthermore, if the galvanizing is not fully “set” or “skinned” the powder coating can be absorbed into the zinc layer, causing other problems. You can always try it to verify if the resultant powder coating will provide the properties you desire.