Thread: Hideous paint failure

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Hello all,

This isn't about painting a car but I'm hoping your knowledge can shed some light on my plight.

I have to paint a large industrial enclosure. It came powder coated grey but I need to change it to a lighter color.

I got an industrial coating called IMRON 2.8HG a two part high gloss polyurethane.

I prepped the entire box by sanding.
I then washed the box with an industrial detergent and a ton of water.

After drying overnight I set it up. I have a Sears oilless 2Hp vertical compressor. I jacked an air fitting into the hose and blew any dust off.

I then mixed the paint 3 parts to 1 as per the instructions.
I adjusted the HVLP gun to give an acceptable pattern and started spraying.

I got probably 50,000 pin holes in the paint job and 1,000 larger holes (fish eyes?). It was suggested that water in the air was the cause.

Dupont said once you have pin holes and fish eyes it can often be "fixed" by one or two more coats.

I purchased a filter/water separator and a large desiccant dryer. I also got an in-line throw away screw it on the gun inlet dryer. I plumbed this all together. Mixed the paint and sprayed it again.

This time no new pin holes appeared but all the bigger fish eyes just kicked the paint out. The paint seemed to make little Christmas trees in the center of all the fish eyes which then just sort of vanished.

Slowly(desperately) adding more paint to cover these holes of course then led to many butt-ugly runs.

I am now sanding the whole mess down to the powder coating again.

My questions are, after considering the history(above), what caused the pin holes? What caused the fish eyes?

I do not want a repeat..

Thanks.

We paint a lot of previously powder coated materials, And we have found that good adhesion is near to impossible with just sanding. Back to your problem of fisheyes, we use R+M's 900 pre cleaner(grease ,wax, silicone remover) work extremely good. Imron is very sensitive to contamination be concerned with what is aroud your paint area and what your air intake is inhaling.

Incorrect prep is your problem. Washing with any detergent will leave residue on the surface that HAS to come off. Rinsing with water will not do the job. Your first mistake was sanding the box without cleaning it first. Any sanding you did has driven oils and junk down into the surface.
This is a process I use when I paint anything that may have stuff on it I don't know about...
1) Wash the item with TSP (Trisodium Phosphate) mixed in hot water. TSP is a cheap degreaser used for washing houses and equipment prior to painting. It can be had at a hardware store for a few bucks a box. Use a power washer if you can and water as hot as you can get it. (The power washer may work for you to strip this paint job also because it has no real "hold" on the substrate. A high pressure wash may strip all of it off. Worth a try?)
2) Wash the surface down with Prep-Sol or Pre-Kleano BEFORE doing any sanding and BEFORE spraying any paint... This is a must... Sanding on a dirty/greasy/oily surface will only make it harder to clean and yo will be surprised how much easier the surface will sand when it is clean...
It sounds like you have a big job ahead of you to make the jop right... good luck.
Mark

Thanks guys.

I shall follow your advice.

"I'm goin in, cover me"

The fisheyes are caused by silicones in the air. Did you happen to use any silicone caulk or gasket maker near the car? Perhaps some silicone spray lubricants were used?

I got the entire thing clean and then sanded it. Then I washed it and let it dry.
Yesterday I set it all up for painting.
I got out an air fitting that is just a quick connect with a hose barb fitting screwed into it to blow off any recent dust.
I jacked in the air nozzle and out comes this huge cloud of water vapor. I stopped and opened the compressor drain. Not a single drop of water came out.
Reinserted the nozzle and pointed it at my stainless bench top. Water rivulets appeared and spidered all over the table.

And this after a $60 filter separator and a $150 desiccant filter... "This is nuts!", I think. So I look at the indicator window on the desiccant filter. Is it pink? Is it blue? No, it's black.... How can it be black? I open it up(a lengthy process of removing nuts and unscrewing a huge collar.

It's empty!! It doesn't come charged with desiccant!!! Argh!!!

So I have to order it: $64 + Overnight/Sat delivery..

I just got it.. Stay tuned.

Hot air cool concrete floor = condensation. Disposable water ball at the gun should fix your problem.

I've painted a couple of sand rails lately, and (as someone mentioned) they have had some pinholing in the powdercoat, which causes the paint to fisheye where it has to bridge over the holes.

Well I got the desiccant and charged the dryer. Wow! You plug in the air nozzle and nothing seems to be coming out but air so dry you can actually feel it sucking the water out of your skin!! I added a disposable water ball to-boot.

I blew it off and painted it. Not a single pin hole or fish eye. I am now happy!

HOTRODPAINT; I could cause pin holes by cranking up the air pressure. I believe this forces air into the paint that then rises to the surface and pops.

Thanks everyone for your help.

Need to use solvent or water based pre clean... That gets any grease off the part and don't touch it anymore after you clean it. Use two rags, one soaked with the pre clean, the other dry to wipe off RIGHT after wiping with the pre clean.
76GMC1500, your comment about the silicone reminded me of something... last year or semester shall I say in my welding class at the local college, the teacher told the class about welding his friend had to do for the government and military on vehicles, chairs, etc. He said that they were VERY picky and things needed to be done PERFECT with no problems and done on time. Well they were TIG welding something and got done and the weld was as perfect as it could get. The inspector came by his shop and looked at the part. He said the part was very good but he cannot take it. He said there were very little black dots the size of a pinhole on the bead (just a few of them). They could not figure it out until one day my teacher went to an old guy and showed him that... The old man asked him "what are you doing to clean these?" He said sand blasting... The guy tells him "well if your sand blasting then you have silicone in the blasting media causing this... That was the problem was the silocone... lol sorry I am off topic but thought I'd share that with you.. Maybe I actually taught someone something.

Thanks Hell. Interesting. Are you saying the welds were polluted or paint over the sandblasted welds was polluted?

Originally Posted by kcress

Well I got the desiccant and charged the dryer. Wow! You plug in the air nozzle and nothing seems to be coming out but air so dry you can actually feel it sucking the water out of your skin!! I added a disposable water ball to-boot.

I blew it off and painted it. Not a single pin hole or fish eye. I am now happy!

HOTRODPAINT; I could cause pin holes by cranking up the air pressure. I believe this forces air into the paint that then rises to the surface and pops.

Thanks everyone for your help.

Sounds like you have what is called Solvent Popping from the top coat drying faster , and the solvents have to push through the top layer and will either leave a small bubble or a PinHole from when the bubble pops .
SprayTech

Why would there be silocone in the blasting media? Or, was the guy confusing silicon with silicone?

(QUOTE) I could cause pin holes by cranking up the air pressure. I believe this forces air into the paint that then rises to the surface and pops.

Interesting theory, but in 40 years I've never seen or heard of this happening. Usually it is a surface contaminent, something coming through the air line, or pin hole. If you've ever painted over bodywork with pinholes in it, you'd know how it looks. As I said, I just had it happen on powdercoat myself, and it was very slightly pinholed. I don't know how it is produced in the powdercoting process, but it was there.

Silicon and silicone are different? Heck if I know, it's one of them but yes the weld itself was a failure. VERY tiny black dots on the weld bead that you could barely see.