Pin hole on cured powder coating

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segatown
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Joined: Mon Mar 06, 2017 6:34 pm
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Pin hole on cured powder coating

Post by segatown » Mon Mar 06, 2017 7:00 pm

Hi,
I'm supply galvanized sheet metal to my paint supplier, since month ago I have an issue with pin holes on cured powder coating.
Up to now, they clean washer system (phosphate), transportation system, oven, paint boot.

They ran production with different substrates (aluminum, cold roll and galvanized) with same powder coating.
Just on galvanized shows the issue.

What can be problem?

Thanks
Adrian

WiseAssYT
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Re: Pin hole on cured powder coating

Post by WiseAssYT » Mon Mar 06, 2017 8:39 pm

It was still dirty ,or had junk imbedded in the galvanized coating that tried to escape during the cure process...
should bake the galvanized above cure temp first , wash ,dry ,and then off to coat it

segatown
Posts: 5
Joined: Mon Mar 06, 2017 6:34 pm
My Location: 92231

Re: Pin hole on cured powder coating

Post by segatown » Thu Mar 16, 2017 1:52 pm

Hi,
Our subcontractor runs a samples with low temp and reduce a lot but not eliminate it.
Powder paint is chemistry POLYESTER TGIC.

Please check info and advise.
In some metals are back issue.

thanks
Adrian
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WiseAssYT
Posts: 853
Joined: Thu Aug 27, 2015 12:16 pm
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Re: Pin hole on cured powder coating

Post by WiseAssYT » Thu Mar 16, 2017 2:54 pm

You have trapped gasses escaping from the galvanized coating,
bake the parts hotter than cure temp and for a longer time than the cure time of the powder , before ever washing and trying to coat it.

You won't get rid of all the pinholes ,unless you use the fusion bonded epoxy primer, but they will go down drastically by just baking the shit out of them before washing and coating.

450 pmt atleast 20min , let cool and then process as usual.

Also curing at a lower temp for longer helps.

All things your subcontractor should know, while also informing you that the pinholes are the side effects of coating galvanized. He shouldn't be shocked or not no how to deal with this.
If you can , find another finisher or shop, atleast one that understands the basics.

segatown
Posts: 5
Joined: Mon Mar 06, 2017 6:34 pm
My Location: 92231

Re: Pin hole on cured powder coating

Post by segatown » Sun Apr 02, 2017 1:06 am

Thanks to all,
After several trials supplier got under control issue, site room environment was affecting material.

Thanks

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