Newbie Primer Questions

Kenzie

Kenzie

New Member
I've done a lot of reading on the forums here, FB groups, and just general googling but I still have a few questions when it comes to how to proceed with my Miata.
I stripped it down to bare metal after realizing the paint and body work was worse than it first appeared. On July 22nd I sprayed the whole car with Omni MP170 epoxy primer (using up a gallon that I had on hand...I've now switched to all SPI products) Since I'm well outside the recoat window (72 hrs with that brand) I plan to sand the car and respray with a coat of reduced epoxy and then proceed with SPI 2K High Build Primer.
1. How long should I wait after spraying epoxy (again, not SPI, Omni MP170) to spray the SPI 2K High Build?
2. Can epoxy primer be sprayed on flexible parts, like the bumpers, without a flex additive? (parts are TPO and ABS)
3. Can SPI 2K High Build Primer be applied on TPO bumpers or will it crack? I have Upol 7061 flexible filler for the big defects but want to avoid having to skim the whole bumper to get rid of all the little nicks and chips on these 30 year old bumpers.

TIA for any advice!
 
Hi Kenzie. Welcome to the forum. To answer your questions in order:

1. Sand with 180 and apply two coats of SPI epoxy. Temps need to be at 70 or higher for 24 hours. After 24 hours you may apply 2K.

2. Yes. SPI Epoxy is flexible on it's own. TPO will require you use an adhesion promoter first. SPI makes a good one. Not needed on ABS.

3. Yes. But a better plan would be to build with SPI Epoxy on your bumpers. It is flexible and will not crack. 2K will crack when flexed. Ideally you would sand your existing bumpers finish really well with 180. Ad-Pro over any bare plastic and spray 3 or more coats of epoxy. Any small nicks that remain you can use regular 2K glaze over the epoxy. Then re-coat with more epoxy. Doing it this way will keep your bumpers from cracking like they can and do when using 2K urethane.
 
Chris_Hamilton said:
Hi Kenzie. Welcome to the forum. To answer your questions in order:

1. Sand with 180 and apply two coats of SPI epoxy. Temps need to be at 70 or higher for 24 hours. After 24 hours you may apply 2K.

2. Yes. SPI Epoxy is flexible on it's own. TPO will require you use an adhesion promoter first. SPI makes a good one. Not needed on ABS.

3. Yes. But a better plan would be to build with SPI Epoxy on your bumpers. It is flexible and will not crack. 2K will crack when flexed. Ideally you would sand your existing bumpers finish really well with 180. Ad-Pro over any bare plastic and spray 3 or more coats of epoxy. Any small nicks that remain you can use regular 2K glaze over the epoxy. Then re-coat with more epoxy. Doing it this way will keep your bumpers from cracking like they can and do when using 2K urethane.
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Thank you! Unfortunately, due to budget, I have to use the Omni MP170 epoxy I already have on hand and can’t purchase SPI epoxy at this time. I wasn’t sure if anyone here had experience with the Omni brand, or if I was even allowed to ask. I know the SPI epoxy is the better product and is one of the star products, but I’m on a tight budget with this car and had to make sacrifices
I will be using SPI 2K High Build, Intercoat Clear, and Universal Clear to finish the car though.
 
Kenzie said:
Thank you! Unfortunately, due to budget, I have to use the Omni MP170 epoxy I already have on hand and can’t purchase SPI epoxy at this time. I wasn’t sure if anyone here had experience with the Omni brand, or if I was even allowed to ask. I know the SPI epoxy is the better product and is one of the star products, but I’m on a tight budget with this car and had to make sacrifices
I will be using SPI 2K High Build, Intercoat Clear, and Universal Clear to finish the car though.
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Understood. Same principles hold true. Although Omni is not on the level with SPI it will be significantly better than spraying 2K on those bumpers. Everything else I wrote will apply.

Here is the TDS for the product you are using. Read it as it will have some good info in it on mixing, spraying, and dry times.

 
dhutton01 said:
Is Omni epoxy significantly lower cost than SPI epoxy? Are you comparing sprayable gallons?

Don
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I think they’re about the same cost…the Omni might be a little more expensive, I don’t remember. But, point is, I already have it and it needs to be used up. I have just enough to do this car and then I’ll use SPI for future projects.
Even if the SPI was more expensive it would be worth it not to have the hassle of unknowns when mixing brands.
 
chis gave good info. omni or spi shouldn't matter really. epoxies are generally pretty flexible so will be fine on your bumper. question is, is the omni epoxy heavy enough to fill your defects on the bumper using it by itself. i have no idea how many coats that would take. spi epoxy doesnt build super heavy either. either way, your bumper will need a coat of adhesion promoter. remember less is more with adhesion promoter. the thinnest full coat you can put on is what you want. applies to any brand. the spi high build will work better for filling but will have less flex. it does flex however. that was my std primer for 20 years on sport bike fairings and i never had it crack on those. if you decide to use that then i would tell you to just sand as much off as possible without cutting through.
 
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