Is it necessary to paint roof?

[TXcharger70]

I was wonder if it is necessary to paint the roof if i am putting a vinyl top on? or can i just leave it primered

[y3chargerrt]

I'd paint it unless you want to see rust bubbles forming under your new top in the future.

[b5blue]

Primer holds water and will promote rust. You want a good paint for the glue to stick well to.

[Silver R/T]

^^^^No paint necessary. Just use good quality 2k epoxy primer. Paint alone does not provide any rust protection whatsoever.

[b5blue]

So you can glue to epoxy primer? (Test areas on my car with just epoxy primer are rusting, too thin maybe.) 

[bill440rt]

TX, put a coat of paint on the roof before you apply the vinyl top for good measure. Epoxy primer will provide rust protection better than other primers, but if you have the paint already in the gun it wouldn't hurt to give the roof a coat or two.
At the start of the paint job I applied a sealer. I then simply gave my roof one coat of basecoat, then one coat of clear just so there was something else on it besides primer. Before applying the top, I lightly sanded it to "de-nib" the paint. Any dirt nibs may show thru the vinyl.
To say paint provides ZERO rust protection is simply not accurate. It will provide better rust protection over primer than just leaving primer alone.

[TXcharger70]

thanks for the replies. The car is painted but the guy who is painted it said it wouldn't be necessary to paint the top, that the primer would be fine. But i  agree that the paint would add some insurance and help seal it better. Now is do i need to apply clear coat as well?

[Silver R/T]

Paint is porous (base coat) Just do experiment yourself. Get a piece of steel and shoot some base coat on it. Leave it out in rain/weather and check back on it in a month or so. There will be rust all over it. If you want to waste paint painting roof go ahead, it's YOUR money. Of course I don't know much, I'm only a painter duh...

[TXcharger70]

So use a paint and clear or leave it primer

[Silver R/T]

Use a quality epoxy primer such as SPI and you're good to go
http://www.southernpolyurethanes.com/Purchase%20info.htm

[FLG]

I agree with silver...honestly id go the extra mile not only use SPI's epoxy but also shoot BB/CC on that sucker as well. You dont want to do things twice...especially expensive things.

[b5blue]

Silver, for all us non-painters....will you briefly explain? (I paint, just not cars) I need a "primer" on automotive primer's then, you have "Poly", "Epoxy", "self etching", stuff like "Rust Bullet" and the black stuff Eastwood sells, then there is the gray and iron oxide deep red type (enamel I guess) so to me when someone said "primer" with no prefix I now see it could be 6-7 different types...... (I'm not even touching on weld through, Por 15, or "base coat being permeable") The reason I'm asking is I have tried some different "primers" on my car and they all end up with rust through, I was hoping to find some type that would hold up and let me use the car while I slowly do repairs to the body here and there.   

[bill440rt]

A poly-surfacer primer is usually hi-build with high pigment content. It is used for filling sand scratches in body filler, minor imperfections, or panel blocking.
A self-etching primer usually is a very thin primer, and adheres very well to bare metal.
An epoxy primer has excellent bonding characteristics. It is the least porous.

The original question to this post was "Is it necessary to paint the roof?", in concern that the vehicle was getting a vinyl top.
The concern was if primer was porous and would let moisture in, thereby causing the roof to rust under the vinyl. Primers have some level of porosity, and if they didn't why would vehicles have paint? Gotta ask, from one painter to another, who the hell just puts basecoat over bare steel???     Nearly all paints designed for automotive refinishing will not adhere to bare steel, you NEED a primer for adhesion. And, if basecoat is porous, then by reason a clear must be applied to seal out moisture. Clear is essentially paint without pigment.

One last comment. Picture this. You're in the booth, paint suit on. The car is all masked up. It's just been sealed and you are ready to spray paint. You have a tack rag. The gun is filled with paint. How much extra time, effort, or material will it take to give the roof one simple coat of paint?? And, if you're doing 2-stage, one simple coat of clear?? 3-4 minutes maybe? And a half a gun of material?
The answer almost requires no thought process. Put some paint up there. It's worth the peace of mind if anything else.

Good luck with whatever you decide. 

[Rolling_Thunder]

I believe the factory did NOT paint the roof - they only used primer...        how many cars have with vinyl tops have rust under them ?   I say just paint the roof as well -  what can it hurt - you're there anyway

[Silver R/T]

A poly-surfacer primer is usually hi-build with high pigment content. It is used for filling sand scratches in body filler, minor imperfections, or panel blocking.
A self-etching primer usually is a very thin primer, and adheres very well to bare metal.
An epoxy primer has excellent bonding characteristics. It is the least porous.

The original question to this post was "Is it necessary to paint the roof?", in concern that the vehicle was getting a vinyl top.
The concern was if primer was porous and would let moisture in, thereby causing the roof to rust under the vinyl. Primers have some level of porosity, and if they didn't why would vehicles have paint? Gotta ask, from one painter to another, who the hell just puts basecoat over bare steel???     Nearly all paints designed for automotive refinishing will not adhere to bare steel, you NEED a primer for adhesion. And, if basecoat is porous, then by reason a clear must be applied to seal out moisture. Clear is essentially paint without pigment.

One last comment. Picture this. You're in the booth, paint suit on. The car is all masked up. It's just been sealed and you are ready to spray paint. You have a tack rag. The gun is filled with paint. How much extra time, effort, or material will it take to give the roof one simple coat of paint?? And, if you're doing 2-stage, one simple coat of clear?? 3-4 minutes maybe? And a half a gun of material?
The answer almost requires no thought process. Put some paint up there. It's worth the peace of mind if anything else.

Good luck with whatever you decide. 

To answer your questions. Yes some primers are porous. Epoxy primer is not once it's activated with proper activator. It chemically reacts with activator and provides moisture/air barrier over the metal thus providing BEST protection for the metal.
Vehicles have paint cause nobody wants to drive primered gray/black cars, people love colors! Why would you put color UNDER vinyl top, unless your vinyl top was translucent?
Epoxy primer will provide plenty of protection if applied as specified, you could put a coat of clear over it if you still worried about it but it won't be necessary.
Painting roof is not necessary-it's optional.

[twodko]

I recently had this same dilemma, after bouncing your question off the forum membership, I choose to give the roof a coat of paint. These cars came from the factory with primer only on VT cars.....not good. Save yourself a redo in the future and put some color up there. You'll be glad you did and no "shoulda, coulda, woulda".

Tom

[FLG]

Silvers is right in the sense if you use an epoxy primer your sealing the roof. But why not just use an epoxy and spray it when you paint the car. Your not talking a lot of extra time or materials and it will only add another layer of protection.

[69*F5*SE]

Paint the friggin roof!  What's the big deal?   

[PA Dodger]

FWIW, When i had my Charger painted years ago (lacquer paint) I was told not to paint the roof for a vinyl top because the paint/glue combination could cause a problem with paint lifting or glue sticking. But there are enough people here who painted their roof before the vinyl top with no problems so I guess it's not an issue. I can't say I've seen many vinyl tops laying on the side of the road recently.

Dan

[bill440rt]

FWIW, When i had my Charger painted years ago (lacquer paint) I was told not to paint the roof for a vinyl top because the paint/glue combination could cause a problem with paint lifting or glue sticking. But there are enough people here who painted their roof before the vinyl top with no problems so I guess it's not an issue. I can't say I've seen many vinyl tops laying on the side of the road recently.

Dan

Dan, most if not all vinyl top adhesives are solvent based contact adhesives. They would probably dissolve or soften the lacquer paint. Ditto for lacquer primers.
With today's modern catalyzed enamels & urethanes there is nothing to worry about, they would not be affected by the adhesive.

[twodko]

69*F5*SE,

Don't be so vague! hahaha

Tom