It mainly caused when the gun and product doesn’t have much space and particles emplacement leads to back ionization. Often, this issue happens in corona spraying guns, because the charging part is placed at tip of the gun, when the powder passes through the tip (on close coating that is less than one feet) the ions are negatively charged and grounded, some particles will jump over and form back ionization. In Tribo charging gun back ionization will not happen, because the powder particles got charged inside the gun (as internal parts of the gun are made up of Teflon). But
The un-coverage of the powder at the corners / bends or on the gap of the products is known as Faraday Cage Effect. This issue normally happens with corona charging guns. With Tribo charged gun, there will be no Faraday Cage Effect.
Yes. It can be removed using highly concentrated Sulphuric acid (98%), but you have to be very cautious when using Sulphuric acid and it is one of the cheapest ways of removal. Other options such as using Methylene Chloride, Acetone are also effective in removal of powder coated parts. Burning or heating of the substrate to certain extent is also another option for removal, but take care of warping.
Effective fluidize of the powder will give you very good flow. Fluidization of powder on the hopper in effective way and controlling system passing air flow will give you good coverage and less wastage