Epoxy frustrations..

[mongocanfly]

Here is my newest problem...
I've sprayed all my body parts with epoxy...for the most part it's done really well...my issues are edges and corners...I'm trying to get the epoxy ready for high build but when I try scuffing edges and corners the epoxy almost wipes off...I think just walking by it with a rag will make it come off..I resand and resprayed these areas several times and have the same issue each time...on the flat epoxy primed areas I've hit with 180g due to the roughness of the epoxy , but the edges and corners I'm using red scotchbrite....now I'm out of epoxy and am gonna have to go get more to do it all over again..
So what's the secret?...

[nsb29]

Corners and edges are always the hardest to get paint on and it’s where it’s always the thinnest. what brand epoxy are you using? How many coats are you applying

[mongocanfly]

I'm using sherwin williams... and based on the fact I cant keep the primer on the edges I've been spraying them with 3-4 coats each time I've redid it...but I can almost wipe it off with a rag...I've tried different angles and dropped the pressure some ...same results every time...
I just talked to a guy that has more paint experience than me....he said just hit those spots with some etching primer from rattle can and put high build over it...I know that's not the correct way but.......

[nsb29]

I thought you said he had more experience than you LOL I think you have an issue with the brand you are using although I know nothing about it I would forget it and by SPI. I would also sand it all down good and make sure there is nothing loose on there you don’t want sum chalky stuff underneath turning Loose

[mongocanfly]

Considering my skill level he does have a few more under his belt..haha... swears hes never had a issue with it...
The sw paint was recommended to me by a couple of real body shops if I was going ss instead of bc/cc
I wish I had known more about spi before I started all this, but at the time ,sw was my best choice.
Each time I've redone this I've roughed it up with 80g and cleaned it with wax and degreaser....I've had no issues on the flatter panels...its just corners and edges...almost like the primer just doesn't adhere to the metal

[MP&C]

Etching primer does not always play nice with epoxy. Epoxy has a slight bit of acid in it, enough to help promote adhesion. Etch primer has comparatively more acid in it as it was designed to help with adhesion problem areas, like back in the 80’s when everyone wanted to coat sheet metal with galv. coatings to combat rust issues. There the extra acid was needed to adhere to the more base PH of these coatings because the paint was peeling off in sheets. The flip side to that is adding too much acid in the proximity of your epoxy is just like the horror stories you’ve heard of ospho residue causing delamination from the acid reacting under the epoxy and lifting. Etch primer is likely to have the same effect, and I’d say you need to find a new buddy for advice.

My first question would be what was done under the epoxy as a prep prior to epoxy? It appears to have a lighter color there, is that also epoxy or some other coating? I will say that the media blasting I have done with garnet media leaves the metal with a nice tooth for the epoxy, and it doesn’t fall off by any stretch. I’m looking at your pics on the small screen on my phone but it appears you have something under the epoxy that is causing the issue, or I’d say a prep issue. Fix the cause, not the result. Don’t resort to your buddy’s bandaids.

And lastly, when I get to a laptop I’ll look at real pictures I can see ...

[mongocanfly]

Thanks Robert ...it was more along the lines of one of the loafers at my shop that said spray it with etch primer...that's not gonna happen though...
All the metal was sandblasted and it only has epoxy primer on it....
Going tomorrow and will get some more epoxy and spray it again..
It's only the edges and corners of the fenders that is the problem...
Havnt had any problems anywhere else on the truck...
If I can get this part done I'm ready for high build
Is there anything else I can do to get better adhesion?

[nsb29]

I agree with Robert stay away from the etching primer, didn’t bring it up because you had already said that you disagreed and like Robert all I have is my phone. From a previous thread I knew everything had been sandblasted. Don’t know how you prepped your parts after blasting or what kind of media you had used. I can see bare metal by enlarging your pictures, what I don’t understand is if you have three or four coats on the edges how you can as you say wipe it off with a scuff pad, makes me wonder if there isn’t some issue with the product you’re using. Before I started using SPI I used PPG and in both cases especially SPI i’ve had to work at scuffing, whenever possible I have always applied my high build Within the window to get a chemical bond so I would not have to scuff hopefully Robert can come up with something.
PS I was wondering why you were scuffing with 80 grit that leaves awful deep scratches that could come back and haunt you, You can bury those with slick sand or Feather fill But your regular 2K primers may not hold them down

[mongocanfly]

Nsb...I was using 180...not 80.....the epoxy on the flatter surfaces is extremely tuff...
The reason I was sanding the epoxy was it had a bit of a rough texture feel to it, and was way out of the recoat window...and I wanted it as smooth as possible before the high build...
They used coal slag at the blasters and my prep was blow everything off and wipe down twice with wax and degreaser..then spray epoxy..
I might would think it may be a product issue if I was having problems elsewhere....but it's just the fender edges that are the issue...
I think it's a operator issue.....
Ive re-done it enough times now that the metal showing is almost smooth... could this be the issue?
I've got some 36g paper i was thinking about hitting those edges with and then shoot epoxy on it....thoughts?

[lupo]

Always paint the edges 1st. I switched to urethane primers years ago.

[nsb29]

Lupo may have a point if you had dry overspray on your edges could cause an adhesion problem. I was wondering if you sprayed it Wet enough

[mongocanfly]

When I first sprayed it I didnt do all the edges first ....it could be a overspray issue...but it was always sticky when I'd do the next coat...I made sure of that...and a couple of these re-dos I only sprayed the edges..so I'm still not sure what's going on...
And wiping the epoxy off may be a bad explanation on my part...but it takes very little effort with red scotch brite to start seeing bare metal

[nsb29]

Three coats should leave a pretty good build, you should be able to scuff it without hitting metal, is this primer real thin? I don’t see why you couldn’t just switch to SPI if you’re out and have to bye more

[tjc]

how long do you let the grease and wax remover dry before you start spraying primer?

[mongocanfly]

The primer doesn't seem to be to thin...
As long as spi wont mess with the sherwin Williams paint I wouldnt have a problem with using it..
W and d dry time was about 30min in the sun...

[tjc]

if you are wiping it down twice you need a lot more drying time, next time try over night.

[mongocanfly]

I dont have a clean room situation ....seems like a lot of crap may accumulate on it overnight...

[nsb29]

Contact SPI and ask them about compatibility. Don’t know what kind of preps-all you are using but 30 minutes would be plenty of time I have always wiped my stuff down just prior to painting and have never had an issue, and you’re not having issues anywhere else. LOL I had a guy tell me one time he didn’t use a preps-all Because he was afraid of solvent pop go figure

[tjc]

after you wipe it down let it sit for an hour or overnight. use tack rag in morning to wipe off dust

[MP&C]

Greg, what is the PN of the epoxy you are using? Now that I look at better pictures, it appears the epoxy in some areas is just sitting on top and has not properly cross linked.. I was looking at one of the SW epoxy tech data sheet, and it called for 200-320 paper for sanding prep on recoats. Also, a red scotchbrite is less selective about how it sands off the primer. A sanding block will allow you to sand off the flats first, then come back and lightly address the corners just enough to remove guide coat. It appears by using the red scotchbrite it is cutting away your corners. So I think part of this issue is the sanding method.

To the bottom left of this panel (at the crease) is where it looks like insufficient cross link, the layer appears it is sluffing off as you sanded, showing a sharp edge of that layer.





Still not sure what to make of this, if it was a cold temperature during application or mixing/incubation issue. To me that small area does not show proper adhesion and may be subject to delamination. you could probably scrape it off with your fingernail, and that is a test I would suggest doing.

Originally Posted by tjc

if you are wiping it down twice you need a lot more drying time, next time try over night.

This comment sounds as if the wiping is done and solvent is left on there to dry. If so, that is an INCORRECT application of W/G remover. This solvent is slow to evaporate so that it can float any impurities to the surface, where it is then wiped with a separate clean, dry cloth to remove said impurities. You should be able to do multiple application/wiping sequences, and be painting 30 minutes afterwards. Have never heard of the need to allow W/G remover to dry overnight. It should be wiped PRIOR TO DRYING with a clean cloth to remove impurities. If it is allowed to dry, all you have done is float impurities to the surface and left them there for a guaranteed fish-eye situation. If I have misread your post, I apologize, but at the least there needs to be better clarification of the process.

[mongocanfly]

Robert...
The epoxy is dp210
At the s&w store they said 180 was fine to sand it with prior to high build
I'm using sanding blocks on the flatter surfaces and switched to scotchbrite for edges and corners
I tried the fingernail test and nothing came loose..
Everything was sanded with 180 prior to the next layer of epoxy
I took some more pics of the edges in the pic if itll help..
I may just be me and my sanding method

[mongocanfly]

This is kinda the profile of the fender lip...if it helps
I'm starting to think my issue is operator error with sanding more than anything....

[mongocanfly]

I had to look to find where I took that pic Robert...is what your seeing where the red arrow is pointing?
The red dots are the inner lip of the fender and the red arrow is actually a run in the primer hanging on the edge from where I took a brush and brushed epoxy inside the fender lip radius where I couldn't spray it..I have sanded it off now though...

[MP&C]

A run/sag would explain it. It looked flatter, like it was a layer that went on dry or something....

Are you sanding in line with the crease/edge, using cross hatch, or?? I think the biggest lesson you should take from this is to sand your flats first and address the radius/corners afterward, and LIGHTLY..... It's just like you'll find with buffing, a crease or edge is quick to cut through as the sanding force gets concentrated against such a crease/edge. For the profile you have sketched, I see three flats that I would sand first and then each adjoining radius to do afterward. If you are not using guide coat, doing so will help you to find more restraint, as you can better see when it is smooth/where you should stop..

[mongocanfly]

I see what your saying Robert...
All the flatter areas of the fender I'm doing crosshatch....but the radiused fender lip I just went inline with the lip...I'd wrap the scotchbrite over the lip and scuff...I see what your saying though..break the lip into 3 or 4 different surfaces and work each surface independent of the others ...GENTLY... the more I think about it and look at it , i think most of what's coming off is on the crests of the radius...just to much pressure on a very small contact area....
I'll shoot some more epoxy on it and give it another shot...GENTLY....
What's your thoughts on grit size to do the lip thatll hold the high build?
Thanks for all the advise fellers...