OK, so I've done several searches but can't seem to find what I'm looking for. My Rallye was hit in the rear at some point in the past. The crossmember in front of the gas tank behind the bumper is a bit mangled. When they replaced the bumper, they just found a chrome one and shot it yellow. Looks fine, but the lightest touch flakes the paint off - and it's not the best bumper to start with, anyway. So I'm going to replace it and do it right.

I have a great, straight core being stripped to the steel and I will get it back fully ready for paint. I just don't know what to use, and I'm not sure how to finish the back side to protect the steel. Some dealer info states that the bumper is primed with a red oxide primer, then a coat of "urethane", then the paint, and then the clear coat. No mention is made of how the inside is finished, or not. As one who is in the paint industry (not automotive, unfortunately), I would assume the whole unit was primed with the red oxide, then completely coated with the "urethane", but then only the outside got the yellow and the clear. This would protect the steel from rust without having to paint all the sides.

So the question is, what are the components, in modern terms, of this paint system? Primer I understand, but what (and how thick) is this "urethane" intermediate coat? Whatever is picked for that will determine the top color and clear coats. Does anyone know the original paint supplier? DuPont? PPG?

Any help is appreciated - what worked for you, what looks correct, etc. I have no fear of a paint booth and can apply most any coating with the proper equipment. What say CO?

 

Following, as I will be doing the same at some point.

 

http://wildaboutcarsonline.com/membe...uction_1-2.pdf


That doesn't help much.



I'm going to go out on a limb here and recommend ditching the urethane entirely and painting the bumper in entirely modern systems with many coats on the front to emulate the urethane's thickness.

 

Thanks, Koda - that's a nicer picture than I have, and a decent description of the coating. I'll have some discussions with my automotive guys and see what they might have in a high build primer coat. The only problem with applying multiple coats is the flexibility of the materials, and you might get cracking. It depends on the product chosen, however.

I've thought about powder coating, if I can get a good match, because that would seem to imitate the "not so smooth" finish of the bumpers with the urethane. I just thought it would be nice to do them the way they were designed.

 

I have a rallye and I am going to paint it with the same paint for the car. I don't think there is any real way to duplicate the OEM urethane coating. Most pro auto paint is a type of urethane anyways.

I suppose originally the color and sheen may have looked a little different between the two, but most everyone is going use use base/clear anyways and that seems to be pretty well accepted. I don't think any show cars get points off for have urethane base/clear as opposed to single stage lacquer.

I also doubt anyone will ever get points off for the bumper matching the car perfectly.

I am going to do:Bare metal, epoxy primer, urethane primer/surfacer, sand re-coat that as needed then base/clear.

Pat

 

You're right in that it's highly improbable anyone can tell much about a paint system once it's dried and cured. I'm really curious about the urethane intermediate coating that GM used - is it supposed to be some kind of absorbing layer? By that, I mean that this coating system needed to be as tough as chrome for the front, otherwise a trip down the highway would result in a ridiculous amount of rock chips. I can see that they could use a coating with just a little "flex" to absorb these little impacts. Honestly, today's base coat/clear coat systems are probably hard enough for that. I've found several high build polyester coatings and a few urethanes, but none that seem to be a part of an overall system yet. I'm hoping to get some answers over the long weekend. It's been impossible to find anything on the internet regarding these bumpers - hard to believe.

 

Remember they call them bumpers for a reason, people bumped them into things. I think GM was just trying to make people think they could be as durable as chrome..

Pat

 

You can have the bumpers powder coated yellow. That will give you a durable finish and the muted matte smooth finish originals had.

 

this was back in the time that the gto and b body pontiacs used those rubber noses.maybe this was olds attempt at that.and after 1 year they said it wasn't worth the trouble.

 

X2. Just paint them and be done with it. You will not put the kinds of miles on it that these cars got back in the day. For absolute sure, DO NOT powder coat them. It will never match. When they are painted you will not see a difference between the original coating and the painted coating.

 

If I had to venture a guess, based on what I've seen on other factory painted parts, Olds likely didn't waste time and dollars on union workers painting the backs. Again, just a guess.