Austin95

iTrader: (22)

Opened my hood after my first couple of rides since the car has been back together to see that all the paint on my LS6 manifold has started cracking I'm not sure why this happened, I sanded down the entire manifold with 220, then 320. Scuffed with SEM soap and a red scotch brite then adhesion premotered before laying down DuPont 2k primer. Sanded the primer with 600 for base and clear coat. So maybe someone knows what went wrong and can correct me so this doesn't happen again. Thanks

VAformula

iTrader: (8)

What kind of paint did you use?

Austin95

iTrader: (22)

Dupont gm black. Everything was shot from a spray gun.

1320Chicken

iTrader: (4)

Maybe you need a flex agent in the paint. Like you would for a bumper, because I doubt the intake got hot enough for it to fail. Just a guess though I really don't know how much expanding and contracting one of these intakes do.

Austin95

iTrader: (22)

Ttt...

LSCha0s

iTrader: (4)

Did you use paint rated for high temps? Looks like the primer did not stick.

67goatman455

iTrader: (14)

loks like your primer shrunk A LOT. did you let it flash off correctly?

custombluebird

don't use the plastic promoter! your going to have to sand it all done sand it with 180 scuff it down , clean it with a dewax and degreaser then lay down some nice coats of primer! if you can see the sand marks after it dries take some 400 and wet sand it smooth. then you can either lay down your base coat or give it another coat of primer that's up to you then it will stick to the plastic and bond together and heat should not effect it!

Austin95

iTrader: (22)

No, I was told the manifold shouldn't get hot enough to effect it. I agree, cause it peeled off in sheets, just trying to figure out why it didn't stick.

Yes, I followed the tech sheets. I laid down the primer with about 10 minutes between coats, then it sat for awhile till I could sand and paint it.

Why shouldn't I use the adhesion premoter? I've seen a lot of people use it to help the primer bond. The DuPont tech sheet says 240 for plastic, so will that be good? Could the paint being too thick have been a problem?

Thanks

ZForce1

You have to use some kind of promoter, you can't just paint on plastic. What kind of promoter did you use? The bulldog stuff that's in the writup in the sticky? I've seen some primers separate (between itself). Not epoxy primer, though.

67goatman455

iTrader: (14)

"Scuffed with SEM soap and a red scotch brite then adhesion premotered before laying down DuPont 2k primer"

did you clean again in between the soap and promoter?

Austin95

iTrader: (22)

Yes, rinsed with dawn and water, dried, wiped with wax and grease remover,and then tach clothed before the premoter.

HotWhipT/A

iTrader: (31)

I wanna say the primer was too thick. You don't need much adhesion promoter either. I like Dupont Plas-Stick!

67goatman455

iTrader: (14)

just had a thought...dont most of the aresols say to do a very light coat of adhesion promoter? possible issue?

Wondered about too thick as well, look at third pic, look how much it shrunk up!

HotWhipT/A

iTrader: (31)

I know with the Dupont stuff, you have to let the adhesion promoter dry for 25 minutes.

black79transam

Boy this has me nervous as I used dupont rattle cans and I'm in the process of painting my intake

67goatman455

iTrader: (14)

had a chat with my boss today actually. he was saying using wax & grease remover on plastic is not a good idea because it pulls the mold release agents and any other oils to the surface. only supposed to use water based stuff or just soap and water

HoLLo

iTrader: (17)

That's scary. Hope it never happens to mine. Previous owner had it done in GM Sunset Orange Metallic. I've never painted an intake, but I know, in the past any success I've had with painting plastic, the material had to be highly scuffed.

Austin95

iTrader: (22)

I'm starting to think that is a possibility as well. I only put on 3 coats, then wet sanded a good deal off. Either way, it looks as if the primer didn't even adhere at all! I used SEM XXX Adhesion promoter.

Yes it did. Could the heat have had something to do with that?

Yep, the second coat has to dry for at least 15 and no more than 30.

Hopefully everything holds up for you man, I know how much work they are to do and I assumed that the spray gun would hold up better than a can.

Never thought of that, it could be a possibility. Especially since it appears that the adhesion problem was between the primer and manifold as the paint stuck to the primer fine even when I wiped that down with the same stuff prior to the base & clear coat.

I think that if it hasn't happened you should be good! But I scuffed the **** out of it with 320. If you look at the picture primer to the primer, nothing is shiny.

Anyone else have any ideas?

67goatman455

iTrader: (14)

soooo, in your pics im seeing alcohol and a 3M box. guessing thats 3M adhesion promoter wipes?