Summary for chip resistance of powder coating Discussion
chip resistance of powder coating is poor is the central issue in this thread, where Karen O'Brien asks about coating hot dip galvanized steel columns, posts, bollards, and bike racks because the powder coating is chipping badly. The reply says the key question is whether galvanizing is being considered instead of powder coating, or whether the parts are already galvanized and then powder coated. The answerer points to the American Galvanizing Association’s information on “duplex coating” — organic coatings applied over galvanizing — and says success depends on specifying the correct galvanizing process and using proper pretreatment, probably zinc phosphating, before powder coating. The advice is cautious rather than absolute, but it suggests that poor chip resistance may be a process/prep issue rather than a flaw in powder coating itself.
Q. I would be very interested in any information regarding the coating of hot dip galvanized steel columns and posts. We are currently powder coating bollards and bike racks and the chip resistance factor is very poor.
Any suggestions?
Regards
Karen O’Brien
engineering – Australia
1999
A. Hi, Karen. I am not sure I am understanding you, but are you looking at galvanizing as an alternative to powder coating, or do you buy these bollards galvanized and then have them powder coated, and the powder coating chips off of the galvanized surface?
The American Galvanizing Association at www.galvanizeit.org has booklets for sale on what they call “duplex coating” — organic coatings on top of galvanizing. It is important to specify the proper galvanizing process, and then to conduct the proper pretreatment (probably zinc phosphatizing). Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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February 25, 2009