Recoating problem

[LouisT]

While trying to recoat over a previously PCed and fully cured 18 ga sheet metal part, I'm having what appears to be "Back Ionization" problems. Ground is good, using the Table top Pro gun set at 70KV, shooting TGIC poly powder, shoot booth clean w/ no stray winds or currents. Tryed to do a light medial blast and same results. Powder shoots on good in one area while others it won't grab or has the Back Ionization stars. Since the gun is only 70 or 100KV, is the kv too high for the recoat or can I do something else. I know I can heat the item up to 400 and shoot it on but that is an idea I'd like not to do.

Thanks!

[jtagger19]

70 Kv should be more than enogh for the secound coat
in fact I use my nordson at 40 -45 for the secound and it works .
apply the secound coat at 150 ,that's a rule I always use with my hobby and professional guns.

back ionisation can happend if the KV are too high and the gun too close or bad powder , since I belive you can't go lower than 70 just try to coat a little farther away and try a diferent powder

also a few weeks ago I started having these stars in the coating but the appered only after curing wich I though might be back ionisation and after 4 days of testing and $400 in parts I change I found the problem was water in the air lines , my water filter( separator) broke.
I change it and solved the problem . verify that you have dry air going to the gun.