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Electrostatic relationships in powder coating

Q. I am interested in your thoughts on the charge of powder particles. I read that fines do not charge as well as large particles but have also read the opposite. Which is it?
Ultimately I need to understand the charge as it relates to mil build for various part geometries. I am trying to lower our average mil build (8) and want to understand the global affects on all our part geometries. We powder coat solid rods, hollow tubes of various OD's, thin gauge flat, aluminum and steel mixed, all going into weldments. 300+ parts all shapes and sizes hung densely together on the line.
What are your thoughts?
Could you recommend a book on particle charge and characteristics?
The powder coating books I have seen have been pretty high level/generic.
SYSTEM: 5 stage alkaline wash --> Dry off Oven --> Primer (epoxy) booth --> top coat (TGIC) booth quick change 30+ colors 12 auto 2 manual --> cure oven

Matthew Jackson
- Delano, Minnesota
December 22, 2011

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Hi Matthew, did you overcome the galvanizing problem?
As to answering your current question, I can e-mail you (I already have this), the most definitive explanation of powder coating I have come across. It does not try to sell you equipment but tries to educate the reader on the various stages taking place whilst powder coating. It covers charging, free ions and their influences on particle transfer, deposition, causes of back ionisation, Faraday Cage Effect, recoating parts and current control just to name some of the information it covers. This is an excellent document that is a credit to the author and the providing company.
As Ted would wrap my knuckles if I provide the information here -- it is too long anyway.
Please contact me if you are interested in obtaining a copy.
Regards
Terry

Terry Hickling
Birmingham, United Kingdom
December 29, 2011

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Ed. note: People who would like a copy of this should follow the link and privately request it from Tery.

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January 9, 2012

Hi William,
Geoff informs me that the info contained within the doc leads him to believe that the author has possibly put his finger on one of the causes for orange peel. There is also a section on surplus free ion collection.
Please supply your e-mail to enable me to comply with your request. Anyone else who is interested please e-mail me with your contact details.
Terry

Terry Hickling
Birmingham, United Kingdom