SPI epoxy over old Dupont Corlar epoxy and 79 Camaro urethane bumper cover

T

TX79Z28

Although I am still such a know-nothing rookie, when I started my 79 camaro project, I knew even less.....like NOTHING. So, I was talked into spraying Dupont Corlar epoxy (which now I know is not really for automotive applications). I had the body shell to bare metal, and sprayed two coats of that stuff. That was almost 18 months ago, and the Dupont has held up great, but I really want to start again, but really don't want to go back to bare metal unless I have to. I still have some minor filler work to do, and found that due to my inexperience, I really sprayed the Dupont epoxy rather thin on some spots.

I want to spray SPI epoxy (2 coats?) and more or less "start over". Question is: Is if safe to spray SPI epoxy over this stuff? If so, what should I use to scuff it up so that the SPI will have a good foundation?

Second question: How far do I sand the urethane bumper covers, and do I use epoxy primer, 2K, and base coat? The back bumper cover is mostly original paint (as far as I know), the front is an Ebay piece that has a couple of small places that need to be fixed (gouges but no holes or tears), what product can I use to fix those spots? It seems to have epoxy primer over it now, but I have no idea how many coats of whatever might be under that. Would I make it smooth (nicks, scratches, etc) and then spray it with epoxy/2K/base or just epoxy/base? Or should I use this:

http://www.eastwood.com/usc-impact-flexible-primer-quart.html

If this is the primer I should use, does it replace epoxy and 2K, or just epoxy, or do I still spray epoxy and/or 2K over it?

Any help would REALLY be appreciated!
 
Here's a link to the TDS for Corlar. It contains strontium chromate, a carcinogenic hexavalent chromium compound. This material is not meant to be sanded (it's for wet-on-wet), but after48 hours has passed, sanding will be required before applying any additional coatings. You must consult DuPont regarding any safety measures which may be required to move forward. I believe wet sanding, then disposing of the sanding sludge while it is still wet may be the best way to protect against inhalation hazard.

If you stick to SPI epoxy as a foundation coat and bare metal spots, and SPI regular 2K for areas that need build, you will be fine from now on.
 
crashtech;6060 said:
Here's a link to the TDS for Corlar. It contains strontium chromate, a carcinogenic hexavalent chromium compound. This material is not meant to be sanded (it's for wet-on-wet), but after a certain period of time has passed, sanding will be required before applying any additional coatings. You must consult DuPont regarding any safety measures which may be required to move forward. I believe wet sanding, then disposing of the sanding sludge while it is still wet may be the best way to protect against inhalation hazard.

If you stick to SPI epoxy as a foundation coat and bare metal spots, and SPI regular 2K for areas that need build, you will be fine from now on.
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Just my luck! LOL So, I would need to wet sand with what grit (80?) just enough to give the SPI epoxy something to bite? Or do I need to remove ALL of it? BTW, what I used was Dupont Corlar 25P (I think it's called 2.1 ST now)
 
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I know absolutely nothing about that Dupont product, so I won't comment on it.

As far as that primer from Eastwood, forget it. Every product that you can get from Eastwood can be purchased someplace else, as they simply relabel other people's products. That is a 1K primer that is not what you want now days. You need to find out what the bumpers are made of and go from there. Some bumpers will require an adhestion promoter because of what they are made of. The cuts in the bumpers can be repaired with any number of 2 part repair products made for that purpose. Sorry, brain fart and can't think of the names of any of them right now. After the repairs, appply SPI epoxy primer and go from there.

Aaron
 
ADTKART;6067 said:
I know absolutely nothing about that Dupont product, so I won't comment on it.

As far as that primer from Eastwood, forget it. Every product that you can get from Eastwood can be purchased someplace else, as they simply relabel other people's products. That is a 1K primer that is not what you want now days. You need to find out what the bumpers are made of and go from there. Some bumpers will require an adhestion promoter because of what they are made of. The cuts in the bumpers can be repaired with any number of 2 part repair products made for that purpose. Sorry, brain fart and can't think of the names of any of them right now. After the repairs, appply SPI epoxy primer and go from there.

Aaron
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I am starting to see that, just like buying a gallon of Zero Rust, and realizing I wasted my money....I guess this hobby is just like the rest of life, a series of learning experiences! I have been a loyal customer to Eastwood, and will not say they sell bad products at all. However, I am finding out that what they claim to be unique to Eastwood, is just like you said, re-labeled items that are much more expensive for the "Eastwood" label. Their tech support is marginal, at best, and that is what started turning me off more than anything else.

As far as the urethane nose, and the proper 2 part repair product, how do I find out what it's made of? I know they call it a flexible urethane bumper cover, but I don't know the exact material
 
The bumper cover should have a designation on the inside as to what material it is, such as "TPO" or whatever.

Aaron
 
we used to use corlar when i worked for viking yachts. very good and indestructible stuff but it is an industrial product. health issues aside, if it were mine i would leave the corlar, scuff with 180 grit and apply spi epoxy over it
 
Well it turns out there are several types of Corlar with different formulas, so you still need to contact DuPont for advice on how to proceed. I think sanding and recoating would be appropriate, but I did not want to give you advice that might expose you or your neighbors to a health risk.
 
OK, since I am starting to get known here for my "frugal" side, here is another question: I will be scuffing the Dupont epoxy with 180 and shooting the SPI (ordered it today) over it. NOT to take the place of block sanding the 2K later, but I have a quart of Dupont 2K primer (buff) and activator that I will not be using, since I am going strictly with SPI primers. So, being that I am frugal, I was thinking about (don't cringe over this one...just trying to think outside the box...keep in mind I am a rookie at this!) shooting the Dupont 2K over the existing Dupont epoxy (that I was going to scuff with 180 anyway) and using it as a guide coat to find all the low spots. The body LOOKS fairly straight, but I don't trust my eye on this, and I figured I could find some of the really bad low spots and fix them before shooting the SPI 2K. I would block sand ALL the dupont 2K, and probably even part of the Dupont Epoxy to metal, which is not a big deal, since I am going over the whole thing with 2 coats of SPI epoxy.

The low spots would have obviously the buff dupont 2K, would I use filler at that time, or wait until I shot the SPI epoxy to start filling the low spots with filler?
 
they are both about 18 months old. They are Nason 421-17 SelectPrime 2K buff, and SelectActivator 483-87
 
I don't know anything about SelectPrime but I'd suggest doing a test panel first to make sure your activator is good. Chances are it is fine if it wasn't opened but depending on how long it sat on the supplier's shelf or in the warehouse it may be at the end of it's lifespan. A test is easy and good insurance, also leave some mixed material in a container and see if it locks up good overnight. I've been bitten a few times by old activators and now make sure it never happens again.
 
Bob Hollinshead;6136 said:
I don't know anything about SelectPrime but I'd suggest doing a test panel first to make sure your activator is good. Chances are it is fine if it wasn't opened but depending on how long it sat on the supplier's shelf or in the warehouse it may be at the end of it's lifespan. A test is easy and good insurance, also leave some mixed material in a container and see if it locks up good overnight. I've been bitten a few times by old activators and now make sure it never happens again.
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I will, but is it really that critical, considering I will just sand all of it off since I am just using it as a guide coat?
 
if it doesn't cure you'll have a gooey mess that won't sand off
 
What about saving it and using it later on some interior pieces, or pieces in the engine compartment and trunk?
I'm sure you will be doing plenty of very small pieces sooner or later.
 
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