Epoxy Primer "Spatter" Question

[RSchofield10]

Good Morning Everyone,

Yesterday morning I went to spray a 1st coat of epoxy on my engine bay. Things started off well but went south in a hurry 2/3 of the way through. I am trying to see where I went wrong so I do not make the same mistake twice as I am a novice trying to learn.

Midway through the 1st coat I started experiencing a lot of, for a lack of a better word "spatter". I know at this point I should have stopped but I wanted to try to figure out if it would clear up and where the source of my problem was. For reference the 2nd and 3rd coat went much better but the damage was already done.

Background information....
Sandblasted metal with coal slag (fine) and then prepped with 80 grit on DA
Wiped down (x4) with 700 and allowed to dry overnight
Tack ragged the following morning
Mixed epoxy 1:1 and induced for 90 minutes
60 gallon compressor set 120 PSI at the wall and 28 PSI at the gun w/ 1.5 tip (gun cleaned before use and after each coat).
Refrigerant dryer after compressor and desiccant dryer on the wall in the garage.

Here are two pictures of the "spatter" from the gun. It definitely was not lint of dirt on the metal. Could low air pressure of caused this? I was using a new air regulator on the first coat and was giving me some problems getting dialed in. For the second and third coat I went back to my old regulator because this was the only variable that changed since the last time I sprayed epoxy and that went fine. I don't know if this is a coincidence or could have been the source of my issue.

Any insight would be greatly appreciated. Also, I am assuming this all needs to be sanded down an resprayed since it is so severe. Is it recommended to sandblast again (since many areas are hard to reach) or better to just hit all the spots with a DA? Thanks.

 

[Jim C]

ok i know you said its not lint or dirt but thats exactly what that looks like. i even see little s shaped ones like a piece of lint. 1 mistake is that you wiped down sand blasted metal. that will pull every bit of lint or fuzz out of a rag or tack rag and it will get caught on the metal surface. never touch a sandblasted surface with a rag. you want to clean it, spray it down with 710 and blow it off. #2 sandblasted metal will typically look textured especially when blasted with coal slag. coal slag embeds itself in the metal and doesnt really come out. you said you put 80 grit on it after the blasting and this certainly helps with all this but its not 100% cure. im sure if you sanded the epoxy down with maybe 320 grit and got it smooth, the second application would be totally different.

 

[dhutton01]

Curious what the overnight temperature was before it was sprayed.

 

[RSchofield10]

ok i know you said its not lint or dirt but thats exactly what that looks like. i even see little s shaped ones like a piece of lint. 1 mistake is that you wiped down sand blasted metal. that will pull every bit of lint or fuzz out of a rag or tack rag and it will get caught on the metal surface. never touch a sandblasted surface with a rag. you want to clean it, spray it down with 710 and blow it off. #2 sandblasted metal will typically look textured especially when blasted with coal slag. coal slag embeds itself in the metal and doesnt really come out. you said you put 80 grit on it after the blasting and this certainly helps with all this but its not 100% cure. im sure if you sanded the epoxy down with maybe 320 grit and got it smooth, the second application would be totally different.

Thanks for the advice.

I will certainly give that a shot. The reason I didn't believe it was lint was because there was none visual to my eye and I followed the same process on the interior of the car and it came out fine, but I know that doesn't mean this wasn't the case.

 

[RSchofield10]

Curious what the overnight temperature was before it was sprayed.

Air temp was 80 and the metal temp was 70-72. I made sure to keep the heat on in the garage 12 hours in advance.

 

[Elwot]

I have seen something similar when I wiped blasted surfaces with "lint free" cloths. Light scuff with a maroon pad and the second application was near perfect. FWIW

 

['68 Coronet R/T]

Another thing I like to do is blow the panels off with compressed air just prior to painting. Here in Arizona there is almost always dust in the air and it settles on everything.

Booth fans running, epoxy induced and spray gun ready, blow it off, hook up the gun and get it done.

 

[texasking]

Tack rag, my guess. Blasted texture will "drag" lint out of any rag.

 

[RSchofield10]

I have seen something similar when I wiped blasted surfaces with "lint free" cloths. Light scuff with a maroon pad and the second application was near perfect. FWI

I have seen something similar when I wiped blasted surfaces with "lint free" cloths. Light scuff with a maroon pad and the second application was near perfect. FWIW

Appreciate the info. I used the DeVilbiss paint prep wipes. I’ll give it scuff tonight.

 

[Lizer]

That looks just like lint on blasted metal to me and I've experienced a similar issue before too. Sometimes just scuffing it with red scotchbrite will be enough to sand out the lint and then you can respray. However if the lint has had several coats sprayed over it, then you'll leave craters so will probably need to sand with something with more grit to remove the lint and then level the epoxy. When you spray it again it should be super smooth.

I also do like Coronet does and blow off the panel one time final time in the seconds right before I spray it.

 

[Donny]

Could that be moisture in the line ?? You have a filter on the gun ???

 

[RSchofield10]

That looks just like lint on blasted metal to me and I've experienced a similar issue before too. Sometimes just scuffing it with red scotchbrite will be enough to sand out the lint and then you can respray. However if the lint has had several coats sprayed over it, then you'll leave craters so will probably need to sand with something with more grit to remove the lint and then level the epoxy. When you spray it again it should be super smooth.

I also do like Coronet does and blow off the panel one time final time in the seconds right before I spray it.

I also appreciate your advice. It seems to be the consensus that it is a lint problem, live and learn.

I sanded a test spot last night with 180, it took a bit but I was able to get the spot smooth. I also try the red scotchbrite and see which works best and get it ready for a respray.

 

[RSchofield10]

Could that be moisture in the line ?? You have a filter on the gun ???

I really don't think so, it has a refrigerant dryer after the compressor and also a desiccant dryer 15' before the gun. I did not have a filter on the gun.

 

[MikeK]

You have way too much gun Fluid also. LOT of orange peel.
Cut the Fluid or Up the Air or both.
What Brand gun you using ?
Some 1.5 are hosers and some are equal to a 1.4 .

 

[RSchofield10]

You have way too much gun Fluid also. LOT of orange peel.
Cut the Fluid or Up the Air or both.
What Brand gun you using ?
Some 1.5 are hosers and some are equal to a 1.4 .

I noticed that as well, that is why I originally thought it could have been a low pressure issue. I am using the DeVilbiss Starting Line.

 

[austincooper]

Just wondering what the correct method is for cleaning media blasted surface prior to 80-grit DA, if even a high quality wipe can cause issues.

 

['68 Coronet R/T]

You also want to make sure your air compressor puts out enough CFM of air to handle the gun you are using.
They require a certain volume of air at the stated pressure for spraying.

I believe the tech sheet for the epoxy primer suggests a 1.4 tip for application.

 

['68 Coronet R/T]

Just wondering what the correct method is for cleaning media blasted surface prior to 80-grit DA, if even a high quality wipe can cause issues.

To be honest, I do not try to clean the blasted metal using any type of cloth or towel. The freshly blasted metal, once blown off with compressed air is clean enough.

The problems come when you handle the panel with your bare hands or get some sort of contaminant on it. In that case, JimC already covered the technique of spraying on 710, which solvent based Wax and Grease Remover, and then blowing it off the panel before it dries with compressed air.

Wearing nitrile gloves while handling panels prior to and while spraying paint is a must.

 

[RSchofield10]

You also want to make sure your air compressor puts out enough CFM of air to handle the gun you are using.
They require a certain volume of air at the stated pressure for spraying.

I believe the tech sheet for the epoxy primer suggests a 1.4 tip for application.

That is a good point as well. My compressor puts out 13 CFM at 40 PSI and that it what my gun calls for. I checked the tech sheet before I started and it stated 1.4 or 1.5 is acceptable for the epoxy.

I honestly tried to research as much as possible so I wouldn't make a stupid mistake but here I am after making a stupid mistake .

 

['68 Coronet R/T]

That is a good point as well. My compressor puts out 13 CFM at 40 PSI and that it what my gun calls for. I checked the tech sheet before I started and it stated 1.4 or 1.5 is acceptable for the epoxy.

I honestly tried to research as much as possible so I wouldn't make a stupid mistake but here I am after making a stupid mistake .

Don't think of it as a stupid mistake but rather gaining experience.