The Stovebolt Site Forums The Shop Area Paint and Body Shop Advice and opinions required

I just purchased the boatswain blue paint for the 37. It is PPG versalon ALK-200. It appears there are quite a few choices of same brand primers, so looking for advice for a semi novice. It’s been years, but I have done a couple paint jobs… And more than likely didn’t do them correctly back then. lol. There was minimal amount of rust and welding, and pretty minimal amount of Bondo used, but there is some. I used rustoleum, automotive sandable primer to spray as I went to prevent rust. Do I need to sand back down to mostly bare metal for an epoxy primer? I did use the same primer under spots of bondo. How much time minimum and maximum before recoating with final color? Is it recommended to sand in between? I am intending to plastic off a portion of the shop for a spray booth and it’s certainly too hot to consider spraying yet so gathering information so I can plan.

I used the PPG ALK-200 on my truck. It sprays nicely and can be used with or without the ALK-201 hardener (but that's kind of hard to find in the small quantities you'd need.) A 1/2 pint can of hardener treats a whole gallon of ALK-200. I used hardener on some of my parts, and not others. Can't really tell the difference. I used epoxy primer I got thru NAPA/Martin Senour paints (PIP-302 see attached tech sheet.) I think it would work over the rustoleum, although when I tried to used a solvent based oil and grease remover on the Rustoleum Rusty Metal Primer, it took it off. There is also a water based oil and grease remover that I'd recommend after sanding your primer with 200 grit sandpaper. The nice thing about the PIP-302 epoxy primer is that you can topcoat it up to 5 days without sanding it. So basically it could be thinned and used as a sealer coat, then topcoated almost immediately. Whatever you use, read and follow the tech sheet for that product religiously.

I also have the primer compatibility sheet for PPG products. Attaching that as well.

thanks Kevin, saved the info. most helpful and most appreciated.

Just a word of caution- - - - -"hardener" additives are "cyano-acrylate" compounds (yes, that "cyano" means cyanide) and the vapors can be absorbed through the skin. If you choose to use them, wear a full-coverage disposable "shoot suit" and breathe filtered air from a source outside the paint booth. Lots of professional painters got severe, permanent nerve damage from exposure to hardeners a couple of decades ago, before the hazards of using the stuff were fully understood.

I taught collision repair and painting in a big high school vocational department for a while, about the time all those hazards were being discovered.
Jerry

Jerry is correct on that. I paint that in the back yard on a windless and less humid day and wear a face mask.

I would finish all of the bodywork and sanding, then choose a non-sanding primer-sealer compatible with the topcoat to seal the Rustoleum, then a sanding primer if you need to fine tune the surface prior to topcoat.

good info. I actually don't intend to use a harder in the final color, but does the epoxy primer contain the same type of hardener? I do have a full suit and respirator I use doing interior house painting. I think I can get a better finish indoors. Just had the scare of losing my whole project being evacuated for a week in Colorado City. the fire came about a 1/2 mile from the house. Aspen Acres fire 100K+ acres 60% contained. Lot of crud in the air and probably will be for a long time. 10K invested so far and not finished but wouldn't compare to the house and shop tools...

Glad to hear your safe and no loss from the fire. Coming with a 1/2 mile and having to evacuate - can't even imagine how scary that really is.

Many weren't so lucky. certainly puts things in perspective as to priorities... how many pair of underwear to throw in the bag. Buckshot, if I'm understanding your response; sand and get as perfect as possible, seal with the epoxy primer, spray over with a sandable primer (non-epoxy, possibly a filler type) within the recoat time, let cure, wet sand maybe 600, then finish coat. ??

Yes, you understand. As long as the epoxy primer does not lift the Rustoleum or react to it with wrinkles, you should be good. When using automotive paints and related products, it's best to choose a brand/type and stay with that line. If you can effectively seal the current products that are on the steel without causing wrinkling/lifting, you can then use a product brand and type to fill, sand, topcoat.

Be careful about getting a prime coat too smooth- - - - -it needs to have a little bit of "tooth" to allow the finish coat to get a good grip. If you want an ultra-smooth finish, wet color sand the top coat with 1500 grit and buff to get the shine you want.
Jerry

400 grit is plenty fine enough for final sanding of primer coats. Jerry’s advice is spot on for your top coat.

kevin are you referring to "400" wet or dry. do you recommend wet sanding a primer filler coat?

After you have sprayed what you consider to be enough primer-surfacer, shoot a quick contrasting primer mist, this will be a guide coat and allow you to wet sand the surfacer until the guide coat disappears. Wet sanding by hand with a rubber block and 320-400 paper will show the imperfections as you sand, the water will keep the paper clean and allow it to cut faster and longer.

Wet sanding with 400 grit is the best approach. As far as the guide coat, it will show you the low spots, which may need additional primer or spot putty. You may not want to sand the guide coat off completely, as you may start seeing bare metal that needs to be bumped down.

And you certainly don't want to wet sand bare metal!

I learned a very valuable lesson about Rust-O-Leum red rusty metal primer.. nothing else really sticks to it, and when you paint over it with something else, its adhesion will fail and you get big sheets of the paint you applied two years ago, blowing right off with compressed air. Ask me how I know..

It's good for frames and tractors and such, but I'll never put that red primer on an auto body surface that sees the sun, again. Worst mistake I ever made on the body of my bus.

You can successfully spray Rustoleum gloss black over rusoleum RMP and it will stay put forever. Probably uses the same solvent in the paint.
I paint everything that is supposed to be black this way and have numerous 1st place show trophies to show for it.
If I am painting pitted metal, I pretreat it with Ospho and clean it up before applying the RMP. The RMP gets along will Ospho treated metal just fine.
I would not trust this method with any other kind of paint though.

I should add.. I used Rust-O-Leum white enamel to go with the red primer. So compatibility wasn't an issue when the white said on the can to paint it over the red. Maybe it's because I sprayed it on with a paint gun and it dried enough in transit that there wasn't enough solvent for it to stay stuck? I dunno, this was back in the ninedees after all ;-) I do still remember sanding all that yellow, probably lead filled, school bus paint by hand to to rough up the surface, because I didn't have any power sanding tools.

Now I just use Sherwin Williams industrial epoxy enamel and a 2" brush, and it's even holding up to PNW moss pretty well.

One trick the oldtimers used was to combine all their leftover paint into gallon cans- - - -not mixing lacquer and enamel, of course, and spray a thin coat of "scrap" paint once they thought their body work was done- - - -then wet sand with ultra-fine grit paper and a small sanding block. Any surface irregularities would show up quickly, and could be corrected before the finish coat was sprayed on. Scrap paint usually ended up being a really ugly green color, BTW!
Jerry