Painting over rattle can primer

[Birdie2000]

Just bought a hood that's in primer, and I found out that one of the previous owners was the one who primed it and it's Duplicolor rattle can primer over the factory paint. I've heard that using "real" base/clear urethane paint over rattle can primer is no good and is asking for it to peel or have other incompatibilities. Is there anything I can do to paint over this without problems, or do I have to sand the primer away and re-prime? Wouldn't care too much except it's a composite hood so it's not like I just sand until I see bare metal, plus the engine bay side with all the bracing is also primed with this stuff. So am I stuck sanding, or is there some way to spray over this without consequence?

 

[monster.]

Man, if it's just the hood, strip the primer off chemically until your down to the base paint. Then clean it, scuff it, prime it with some high build, base, then clear?

I wouldn't sand the rattle can primer off of a composite hood, but you could use some stripper, thinner to get it off.

EDIT:

I'm no pro, so I could be looking at this entirely wrong.

but, dont' you love the new paint and body forum, I do

 

[eda50]

It's a 50/50 whether it'll work or not. If the previous guy cleaned and prepped everything right before he primed it, the under coat may hold up just fine. If there were any contaminants still on the paint, it could wrinkle up when you spray anything else on it. If you don't want to have to have to have major problems durring basecoat/clearcoat, you may want to sand as much of the old primer off as you can and re-prime it with a quality primer after cleaning the surface with wax and grease remover. As for the underside, I would chance it with the primer there. I would cut the underside in first after scuffing the exsisting primer thoroughly, and ceaning well with wax and grease remover. Any paint sticks to pretty much any primer. Paint and sealer uses a mechanical bond. It ust needs to be scuffed in order to hang on to the surface. The problem is when the solvents from the paint you are spraying, pulls cheap primer off of the surface it was sprayed on to. I have used that rattle can primer, and gone over it with basf base/clear with no problem. I have also seen when a surface is not prepped correctly. The primer wrinkles up, and pulls off of the un prepped surface. Hope this helped.

 

[smooth]

If you spray over rattle can primer it will probably lift, due to the fact that refinish paint is loaded with strong solvents. Try wiping the hood down with some lacquer thinner, it should come off.

 

[slideways]

If you spray over rattle can primer it will probably lift, due to the fact that refinish paint is loaded with strong solvents. Try wiping the hood down with some lacquer thinner, it should come off.

x2 Wipe it down and it should come off pretty easily. Let sit for awhile then sand the rest off when your prepping it for paint.

 

[Birdie2000]

Thanks guys!

 

[SVT32VDOHC]

Sand it off...period. Too many types of rattle can primer to take a chance. What will happen is that it will bleed through your nice bc/cc paint job. It will look terrible. Strip it down to the old original paint finish sand it, then spray it with your primer and paint.

 

[smooth]

Sand it off...period. Too many types of rattle can primer to take a chance. What will happen is that it will bleed through your nice bc/cc paint job. It will look terrible. Strip it down to the old original paint finish sand it, then spray it with your primer and paint.

Automotive spray can primer is lacquer based, hence the quick dry time.If he wipes it with thinner 97% of it will come off, it will make the job 10x's easier and a lot less sanding.

 

[slideways]

Automotive spray can primer is lacquer based, hence the quick dry time.If he wipes it with thinner 97% of it will come off, it will make the job 10x's easier and a lot less sanding.

:nod:

 

[SVT32VDOHC]

Automotive spray can primer is lacquer based, hence the quick dry time.If he wipes it with thinner 97% of it will come off, it will make the job 10x's easier and a lot less sanding.

True. I had a fender blasted at Strip-It and he put some garbage grey primer on there. Instead of stripping it off, I primed over it with my 2K Urethane primer, then finish sanded before paint and I sanded through a couple spots to that grey stuff. A month after the bc/cc paint job I did, it just started shrinking and eating through. I'm guessing he used an enamel primer.

Either way, laquer thinner to wipe it or sand it off. Most cheap primers buzz right off with one peice of 320.

 

[blk-sunshine]

I second sanding it off. While I didn't have this happen exactly, I had a very similar situation happen. I had previously touched up the black belt line stripe with a can of bumper black. It looked great, I didn't sand it off enough and as soon as I hit it with sealer it bubbled up something fierce. Once you get started painting like that and you have a chemical reaction, I don't think there is anything you can do but let it dry to sand it off later.

 

[blk-sunshine]

Whoops, just noticed this thread was ancient.....still applies though.