See Powder Coating Surface Defects and How to Avoid Them for a detailed explanation of contamination defects and what to do to prevent them from happening..
In this article here, you will find examples of common coating defects and how to correct them. Powder coating defects come from several different types of coating processes:
Powder coating
Automotive assembly plant paint shops
Plastic parts molding and painting facilities
Metal parts casting and painting facilities
 Weld ball in e-coat |
 Copper shaving ine-coat |
 Metal shaving in powder prime |
 Prime oven condensate in metal prime |
 Multicolored paint chip in base coat |
 Masking tape residue in basecoat |
 Blue cotton fiber in basecoat |
 Rust in basecoat |
 Overspray particle in clearcoat |
 Rust in clearcoat |
 Blue synthetic fiber in clearcoat |
 Clear synthetic fiber in clearcoat |
Source: Paint Performance Consulting
Additional sources of information on powder coating defects and how to avoid them:
Troubleshooting Guide to Powder Coating (pdf) by Tiger Drylac
