Paint prep...leave factory primer...or go to bare metal?

[lumbee]

Sup dub lovers and paint/body freaks!

I have finally gotten so disgusted with the paint on my 71 Super (savannah beige) I have decided to do something about it. I am going all in...got my Horrible Freight HPLV Purple gun and have been reading up an paint/process ect. Yes, this is my first paint job

So I am starting to look at paint prep and how I want to approach it. I don't want to mess with chemical stripping. The current paint job is the stock original paint. I have touched a couple of areas with a sander and also a wire wheel (still deciding which of those I want to us). Here is a pic of an area that I took down to the primer:

https://photos.app.goo.gl/th4zNMn7Cf8dChX18

The vast majority of the surface of the car could be taken down to this level of stock primer rather than bare metal. Would this be advisable? I still plan to shoot the entire car with a fresh coat of primer...will new primer bond to this OK? You always here "nothing like the stock paint job" so just wondering if it would be more durable to leave the stock primer underneath...and if I would get a good bond with the new primer I lay on top of it.

The rust spots on the car look like this:

https://photos.app.goo.gl/fxBP6Kscn9W78xWs9

This spots would be taken down to bare metal and primed over with the new coat of primer...obviosly sanding everything down so the bare metal spots match the rest of the car that I may leave the stock primer on.

[Evil_Fiz]

I previously asked the same question. After not getting any authoritative answers (valuable information WAS provided by others) I decided to strip the entire car to bare metal. My reasoning was that there may be hidden "Factory Rust " lurking beneath the primer and/or sound deadening. My fears were confirmed in several locations so I feel good about my choice.

EDIT: A Harbor Freight stripping disk on the angle grinder will be more effective than a wire brush.

There are many areas in the car where mechanical stripping will be very difficult or impossible. After starting out doing mechanical stripping, I experimented with CiriStrip paint remover. I was able to strip four layers of paint with every medium application (medium = 1/8" - 3/16" thick.) I chose CitriStrip because is it non-toxic, biodegradable, and won't burn your skin on contact, even with moderately extended contact. Stripping the car to bare metal is a labor intensive process but does not involve too much additional effort beyond stripping down to factory primer.

My process was/is as follows:
- Apply Citristrip
- Cover with plastic grocery bags to reduce evaporation
- Allow it to work for 12 - 24 Hrs.
- Scrape with a narrow putty knife or razor blade or scrub with a scouring pad
- Hit with a wire brush on the angle and/or die grinder to remove the stubborn spots
- Wipe bare metal with Eastwood After Blast/Ospho/Kleen Strip Prep & Etch
- Klean Strip Prep & Etch is available at Home Depot. and CitriStrip is available a Lowe's

On a 1970 Karmann Ghia convertible it has taken me just under 2 Gal. of CitriStrip to do the entire exterior, interior, engine compartment, trunk and nose area, and inner rear quraters both in the engine compartment and the interior. The wheel wells, front bulkhead, underside of rear parcel area, and under rear seat area remain to be done. I have also gone through 3 scouring pads, 2 Harbor Freight three inch cup brushes on the angle grinder, a pair of HF two inch cup brushes on the die grinder, and about 50 pairs of 9 Mil, nitrile gloves. You can see my results starting at the following post on my build thread: https://www.thesamba.com/vw/forum/viewtopic.php?p=8839294#8839294

Make certain the metal prep product you use is compatible with whatever primer product you will be applying on the bare metal.
Example:
Eastwood After Blast is not compatible with Southern Polyurethane Inc. (SPI) epoxy primer but specifically applied Ospho is.

-----
Emil
_________________
“…It's not just about what's interesting. It's also about what's helpful, and it's helpful even if it helps just one other guy working on a Ghia.”
kiwighia68

See my build on TheSamba at:
The K_R_A_K_E_N_N : a 70 Ghia Convertible reinterpreted

[lumbee]

Thanks for sharing Emil. Made some good progress yesterday and today. I added a few more pics here:

https://photos.app.goo.gl/hgPsEXDd6HbvLxah7

I am finding getting to that grey coat is not easy, there is a layer of brown primer underneath the grey and that is where the wire wheel seems to be landing. I am thinking I will take it down that brown layer (with some bare metal bleeding through) then hit that with 150 grit orbital sander to smooth it out, then prime on top of that.

[theKbStockpiler]

Why don't you try to brush on 'AirCraft Paint Remover'. I'll bet it will take off original VW paint easy. There is that risk of cancer though.http://www.kleanstrip.com/product/aircraft-paint-remover

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Use all safety devices including a mask.

[lumbee]

I may give a chemical strip a try... it's coming along pretty good so far without it though.

[Mike Fisher]

Chemical stripping would be a lot faster than mechanical stripping with all the sanding dust.
Do 1 fender at a time if you're still driving the car.
Leave the original primer on if it's not rust bubbled & just sand it all with 320 grit.
_________________
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69 FI/AT square Daily Driver
66 sunroof,67,70,71,71,71AT,72,72AT,73 Parts
two 57 oval ragtops sold
'68 Karmann Ghia sold

Society is like stew. If you don't keep it stirred up you end up with a lot of scum on the top! - Russ_Wolfe/Edward Abbey

[lumbee]

...that single wheel well took 45 minutes...and my hands were buzzing for 30 min afterwards. The door panel was theraputic...but now I just want it done. I'll get some chem strip a try

[lumbee]

Hey folks. My paint progress is moving along at a moderate pace. Everything in moderation

Here are a few pics of what looks to be thin coats bondo on a few of the sections. However, the paint looks to be factory paint, and also nothing seems to have ever been in a wreck:

https://photos.app.goo.gl/xprDY9eYJ41U39va7
https://photos.app.goo.gl/X3Wm7N7BUyFNZvjS6

Is it possible it would have come from the factory like this? A google search turned up this:

http://www.spiegel.de/fotostrecke/bildband-zeigt-b...750-8.html

...the caption is translated to English with something like:

[Cour6396]

Hi, buy the aircraft stripper, buy some plastic for bagging off cars for paint, and spread the stripper in a pretty copius amount. Spread the plastic over the part, and let the stripper do the work. It locks in the solvent smell, and holds down the stripper to force it down to the bottom of the substrate.

[lumbee]

Shot some primer over the weekend. Here is what I used:

https://smile.amazon.com/gp/product/B000Q8GFPK/

Was real happy with how it went on; here are some pics:

https://photos.app.goo.gl/7zWFQTpVsygikBRy6
https://photos.app.goo.gl/bc3P9vun8emyobhD6

However, was still tacky to the touch after 24 hours. Tried sanding some the next day and it was coming off in little balls. Any suggestions on what I might have done wrong? Added the harder as directed. It was about 55 degrees out on Saturday, so I would have liked it to be a bit warmer. I did let them sit in the sun some on Sunday.

[Cour6396]

Hi, did you let the primer coats flash to dull before applying another coat? How many coats did you apply? If more than three coats was applied, you’ll have to give it more time to cure.

[lumbee]

Uhggg!!! Was out in the garage looking at everything and realized that I forgot to put the water/oil filter on the gun before I sprayed

I am guessing that would cause the paint not the set right...water or oil mixed with the paint would cause this?

Cour6396 to answer your question I did 3 coats with 5-10 minutes between coats.

[Cour6396]

If the primer wasn’t actimg like there was contaminants in the line, you might be okay. If the primer was flashed, the dry time shouldn’t have anything to do with contamination. You were probably just warm enough to not have a problem, at least right now. Later on, they’re might be trapped water in the primer, and will cause time blisters of moisture later, of course, after paint is on. I would open up with your initial block, and let sit in a warm, dry climate for awhile.

[carlos_magnum]

I agree that using chemical paint stripper makes the job easier though a bit messy.

[lumbee]

Sup fools! Just thought I'd post some pics of the [almost] finished product:

https://photos.app.goo.gl/gNzt6LeaKbZDcy6M9

https://photos.app.goo.gl/m4N3ZmNayhYo37X78

https://photos.app.goo.gl/bLMxdBkqV77TkfEg6

Real happy with how everything turned out. Could have stood to do more body work/prep, but this was my first time so I had to draw the line somewhere. Was hoping for a little smoother finish out of the paint gun (note the orange peel in the last two pics) without sanding/buffing, but my paint guy said thats about as good as it will get.

I had fun with this whole process. It was a bit stressful, but that is to be expected the first time you do anything like this. Biggest lesson learned was with the paint gun. I went through two Horrible Freight purple guns and purchased devilbiss gun for the final color. The HF guns laid down the paint as good as the devilbiss, but after about two cleanings they would have issues.

I think I am going to just go with this on the car rather than sand/buff. I can do that down the road if the spirit moves me. I did paint a gas tank with this same color. I am going to sand/buff the tank. I will post some pictures of that when I am done with it.

[Mike Fisher]

Looks good but would look better if you wet sand it with 2000 grit.
_________________
https://imgur.com/user/FisherSquareback/posts
69 FI/AT square Daily Driver
66 sunroof,67,70,71,71,71AT,72,72AT,73 Parts
two 57 oval ragtops sold
'68 Karmann Ghia sold

Society is like stew. If you don't keep it stirred up you end up with a lot of scum on the top! - Russ_Wolfe/Edward Abbey