Priming process?

[DreKoushRanada]

Can you all chime in on my priming process I want to use. Keep in mind I have to pay to get the vehicle towed to the paint booth. My compressor at home is only a 21 gallon Harbor Freight special.
Here is my proposed plan.
1. Finish metal work and the spray(scrub) phosphoric acid on rust spots and pressure wash off while acid is still wet.
2. Dry with lint free paper(shop) towels and sand with electric orbital sander 80grit. I also have clean and strip disc also.
3.. Tow to paint booth. Wipe clean with SPI waterborne W&G remover and then SPI Solvent W&G remover.
4. Spray body in 2 coats SPI Epoxy let sit for 24 hours in paint booth.
5. Spray 3 coats Evercoat Slicksand or if something is better do suggest it.
6. Tow back home to do blocking and filler work while using a guide coat.
7. The grits to use for the blocking procedure gets a bit fuzzy. I was thinking 180, 220 for the Slick Sand.
8. Tow back to paint booth use same prep procedures and spray with 2 coats of SPI 2k primers. Tow back home and block . Not sure on exact grits but want to finish with 600 grit wetsand. Color is Ford Dark Shadow Grey.
For epoxy and 2k primer I have the HF Professional set.
The SlickSand(or similar) will be sprayed with this https://www.amazon.com/TCP-Professional-Gun-auto-Primer-metal-Regulator/dp/B001NOU92G
I will be buying a Iwata LPH400 for base/clear

[jlcustomz]

This may be one of the most opinionated subjects out there.
I know some of your procedure you are adjusting to having to be towed to spray booth back & forth.
I've been on spi forum for a while myself& starting to use their stuff. First of all, it would really be better to get another day of dry time with epoxy before spraying with poly primer. Possible issues could be cracking or adhesion issues.
Much different opinion on primer usage, but you definitely want enough dry time after epoxy & coating epoxy before 7 day window time & respray epoxy on epoxy with over 7 days dry time for adhesion, can be a reduced epoxy coat , which will be smoother & not require as much dry time. A reduced coat of epoxy as a final sealer before actual paint adds adhesion. Definitely want to spot spray epoxy if you hit bare metal during the bodywork process. Items in this paragraph are pretty consistant among spi users.

Lots of opinions on primers. I've used g-2 in the past & there was a thread a few weeks ago on spi about the newer evercoat poly primers, I think it was Chris Hamilton commenting on one of the newer grades being his favorite. To me one of the main things about poly primer is being able to take the place of slathering a whole car with a skim coat of filler. this stuff sprays on rough & sands smooth, which makes it work as a guidecoat. As with any body filler, you pretty much want to sand off all that isn't needed without. Early in the blocking process of a poly spray filler I d skim coat areas that appear to need more filler as soon as they start showing up, such as you'll likey find where you shaved your driprails.
As you know, a poly primer needs a good sealing. Some spi members don't even use 2k primers, they do a couple of standard epoxy spraycoats over it, let It dry , blocksand it, then do the reduced epoxy coat before paint.
Some spi members only use 2k primers. If you have a body in much straighter condition, the 2k primers aren't as nasty to fool with. Poly primers use mekp as a hardner & have that strong fiberglass styrene monomer smell. With 2k primers you don't want to overuse them on spots where you really need to apply more bodyfiller, this is how you can end up with shrinkage spots showing up after job completion.
Some people start out with 2k primer, use standard bodyfillers where needed, a little more 2 k over it, then use the poly primers over it as a final long block sanding step. All a matter of opinion. Just don't do any wrong steps in your process.

If you have some areas that definitely need more body filler work while the rest of the body is pretty good, you could epoxy those areas at home first, hand apply body filler after 2 days, sand & epoxy again to cut down on work time between having to go back & forth between booths.
Just a few opinions.....

[DreKoushRanada]

This may be one of the most opinionated subjects out there.
I know some of your procedure you are adjusting to having to be towed to spray booth back & forth.
I've been on spi forum for a while myself& starting to use their stuff. First of all, it would really be better to get another day of dry time with epoxy before spraying with poly primer. Possible issues could be cracking or adhesion issues.
Much different opinion on primer usage, but you definitely want enough dry time after epoxy & coating epoxy before 7 day window time & respray epoxy on epoxy with over 7 days dry time for adhesion, can be a reduced epoxy coat , which will be smoother & not require as much dry time. A reduced coat of epoxy as a final sealer before actual paint adds adhesion. Definitely want to spot spray epoxy if you hit bare metal during the bodywork process. Items in this paragraph are pretty consistant among spi users.

Lots of opinions on primers. I've used g-2 in the past & there was a thread a few weeks ago on spi about the newer evercoat poly primers, I think it was Chris Hamilton commenting on one of the newer grades being his favorite. To me one of the main things about poly primer is being able to take the place of slathering a whole car with a skim coat of filler. this stuff sprays on rough & sands smooth, which makes it work as a guidecoat. As with any body filler, you pretty much want to sand off all that isn't needed without. Early in the blocking process of a poly spray filler I d skim coat areas that appear to need more filler as soon as they start showing up, such as you'll likey find where you shaved your driprails.
As you know, a poly primer needs a good sealing. Some spi members don't even use 2k primers, they do a couple of standard epoxy spraycoats over it, let It dry , blocksand it, then do the reduced epoxy coat before paint.
Some spi members only use 2k primers. If you have a body in much straighter condition, the 2k primers aren't as nasty to fool with. Poly primers use mekp as a hardner & have that strong fiberglass styrene monomer smell. With 2k primers you don't want to overuse them on spots where you really need to apply more bodyfiller, this is how you can end up with shrinkage spots showing up after job completion.
Some people start out with 2k primer, use standard bodyfillers where needed, a little more 2 k over it, then use the poly primers over it as a final long block sanding step. All a matter of opinion. Just don't do any wrong steps in your process.

If you have some areas that definitely need more body filler work while the rest of the body is pretty good, you could epoxy those areas at home first, hand apply body filler after 2 days, sand & epoxy again to cut down on work time between having to go back & forth between booths.
Just a few opinions.....

Thank you for taking the time out to answer my questions. I will most certainly look into spot priming for sure. I can leave the car in epoxy for 2 days before spraying. That won't be a big deal. The major dilemma is we are not able to do any sanding at the Auto Skills Center (Army base). I guess somebody sanded epoxy out side the spray booth and the environmental team seen it and had a fit. They actually had to sweep the grass. Haha. So one numb skull ruined it for everybody.

[dhutton]

I like to use Z-Chrome Rust Defender for poly primer. I recommend the SPI Turbo primer instead of their 2k primer. Otherwise your process looks good. The Rust Defender is my final primer aside from reduced SPI epoxy sealer before base.

Don

[HotRod47]

I can't speak on SPI products as I have never used them. But, I have a couple other things to add.

Like stated above, I would recommend letting the epoxy sit longer than that before spraying a poly over it. Epoxies by nature are slow cure. Don't want any issues down the road. Again, without knowing their system I would read a tech sheet or call the owner and ask what his recommendations are in that situation. Safe rather than sorry kind of thing.

As to the sand paper grits, I start my blocking with the poly at 100, maybe 120. Remember, the courser the paper the sharper the cut. Translation, the courser the paper the flatter the panel. Bring that up to 220 if it were me, then spray your primer surfacer. On surfacer I start my final block with 320 dry, then guide coat, 500, then quick hit with 600 if I am not going to use a sealer.

Thats my process for what its worth. See my project in that section to see what I am doing.

Good luck.

[Rucumn]

Just a couple quick comments....

No need to go from 180 to 220. I usually go from 180 up to 320, but if you are spraying a 2k over the polyester, then just leave at 180 for the 2k. You will be sanding the 2k anyway.

Also, if you are spraying a metallic or pearl of any kind, be sure to sand your sealer for much better results. Do not spray a sealer just prior to the metallic, unless you sand it with 600 grit first.

[DreKoushRanada]

I appreciate you all stopping by. I seems like bodywork and paint is the longest part of a build. Everything else will be a bit of a breeze after this task.