Fisheyes and pinholes - please help!

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mag911
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Fisheyes and pinholes - please help!

Post by mag911 » Sat Apr 04, 2020 4:47 pm

Hi guys, my dad and I own a powder coating and wheel repair shop and have been recently having trouble with fisheyes. Long story short with the changes in weather we noticed moisture in our air system so we went all out and got an air dryer, 3 stage filtration with 2 desiccant filters (one out of the dryer and one right before the powder gun). We use a Colo manual system and manly spray hot because this gun doesn’t lay powder smooth unless applied pretty heavy (gloss black only looks mirror around 8mils).
We have had very good results but recently started getting fisheyes IN EVERYTHING!
We hang wheels from the valve holes, like most of you and noticed the fish eyes manly appear in the 6 a clock position opposite to where we hang which leads me to believe something is being brought down by gravity, likely during outgassing and remains there before spraying.
Since we use a professional chemical stripping tank, we dont blast everything unless we need to, so we outgass before spraying not before blasting. We do however pressure wash and scrub with detergent before outgassing. We tried Alcohol wiping or just spraying and the fisheyes still appear. We eliminated all silicone sources from the shop.
Today we sprayed 4 wheels, 2 of them got pressure washed without scrubbing and 2 of them got scrubbed and rinsed properly. 2 came out perfect, one had pinholes all over and one had fisheyes in the 6 a clock position.
Has anyone experienced fish eyes and powder contamination because of detergent or soap residue? It is honestly my last possible explanation for this...
thank you so much!
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duke46
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Re: Fisheyes and pinholes - please help!

Post by duke46 » Sun Apr 05, 2020 10:14 am

The powder coating system you have should be able to apply powder cold and a few of the guys on here have or have used one. Do you have a dedicated 8' ground rod placed right outside your shop or maybe through your floor? If it is through the floor then it needs to be damp and that can be true for some guys that have them outside also and have to keep them moist.

With you saying that two wheel came out good and two came out with fish eyes makes it harder to chase down a problem unless it is in your prep at some point? Fist of all you never ever want to wipe down something that has been media blasted and you are just asking for trouble. Before coating it is best to use a hand held torch to go over the item to get rid of any fuzzes.

Is your oven electric or propane or NG? One of our guys that had a propane oven that worked fine and then he started having troubles like you are I think? What they found out was it was caused by the propane the gas company had used to fill his tank with. They came and got his tank and installed a new one then filled it with the proper gas that he needed and after he purged the lines every thing was back to normal.

When I am going to coat any thing that has been painted or coated I chemical strip the item then I wash off and let dry. Next I media blast the item and then blow it off really good and then most all the time I will just take it to my bay and coat and used no other prep. I do have a dry product that mixes with water called metal wash I buy from Eastwood and I will just wet the item after blasting and blow it off and then once I am sure it is dry I am ready to coat. It does a great cleaning job and that is what is made for. Some times I will also spray an item down with acetone and it will help get rid of any oils that might have been on some ones hands. Some guys will use denatured alc and it also work fine but takes longer to dry. Most of use the small pressurized bottles to apply it.

Well that is about all I have at the moment?
All I have said is said just for meanness so I don't have to argue with anyone!

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mag911
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Re: Fisheyes and pinholes - please help!

Post by mag911 » Sun Apr 26, 2020 7:47 am

Thank you SOOO much for taking the time to respond! Yes we have a 8’ ground rod through the shop floor, yes we wet it. After more diagnosis we redesigned our final wash process and it solved everything.
We also got to demo an Optiflex 2 for a week and I can say with confidence there is NO difference in the quality of finish being applied. We are therefore redesigning our curing rack to hold wheels in a horizontal position, keeping our Colo station and continuing to shoot hot. I will post updates in this thread for the sake of archiving for other people.

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