Next week, I will be getting my Skylark body back from sandblast and I would like to shoot it in primer to prevent rusting while I finish the work. It will take a few months to patch and repair some floor sections as well as the cowl panel and rear window channel. Would Epoxy primer be the best or should I go with a urethane? Will sitting for a few months cause issues with topcoat adhesion? Any advice would be appreciated.
The best thing you can do is shoot a couple coat of epoxy primer on it as soon as you get it back. Just make sure it is clean, clean, clean before you shoot it. You can do all your bodywork over the top of the epoxy primer, just scuff it first. You said it is being sandblasted? I hope your sandblast guy knows what he's doing because a sandblaster in the wrong hands will ruin the body sheet metal on the car in a hurry.
I like the Epoxies too. Bill what brands do you like? The name-brands are getting WAY too expensive. You'll eventually need a sandable primer/surfacer to fill in minor imperfections. 2-part urethanes are a good choice there. You can apply them over a sanded epoxy primer.
From what I have heard, everybody that's mentioned using Southern Polyurethane brand epoxy primer has had great results. It's probably much more affordable than the big name brands. I also read about many people using other name brands, that were able to use laquer thinner and wash off supposedly cured epoxy primer. But people that tried that with Southern Poly. did not have that problem. After reading about that, I tried the test on some of my parts that had sat for many years and was able to get it to wash off. I don't want to name names, but it is one of the well known brands. It may not really be a valid test, as it's not simulating anything that's going to occur during the priming and painting process. And some of it may be actually designed into the product to promote intercoat adhesion.
No matter which epoxy primer you choose, prep the bare metal first, with any one of the phosphoric acid based products available, and follow the directions for their use. Corrosion will have begun on all surfaces of the sheetmetal after the blasting, even if it isn't visible. You may have to acid prep and prime one panel after the next. Nothing wrong with doing this in stages. Prep one area, neutralize it, clean it, then go for epoxy primer. I's ok to do that one surface after another if it's convenient. Devon
You should DEFINITELY check with whatever the manufacturer has to say about using one of the acid-based prep materials under their epoxy. Some say it's "OK", some say "NO", others say "OK...but not if the metal has been sandblasted". This is the FIRST LAYER of material over the bare metal so make sure you get it right and follow the recommendations of the manufacturer. Also--you said it will be "sitting a few months". Hopefully inside. In any case, again, I emphasize following the PAINT MANUFACTURER'S directions. You will likely find that all of them recommend cleaning and scuffing the epoxy and shooting a fresh coat over the old epoxy before applying any more primers/paints if the epoxy has been on the car for "X" number of days (typically 7 days or so). You really need to get the "P Sheets" (Product Information Sheets) for whatever paints you are considering using and read them BEFORE you buy the paint and/or apply it. You can download them from the paint manufacturer's website or get them at the paint supply place for free.
I've heard good things about Southern (SPI) as well. Their clears are popular too. I used Omni in the past. Stopped using it when they changed the formula and switched from the 1:1 mix ratios. I don't like having unused hardener sitting around going bad. I've been using epoxy primer and black topcoats from Viking paints. JW recommended the black epoxy for chassis parts years ago. 1:1 mix ratio and it's easy to adjust the gloss. Nice product! Interesting. I have read self-etching primers should not be used with certain metal conditioners. Anytime I sandblast, I always go over the part with a DA sander to further smooth the metal. A blasted surface is difficult to wipe down... It holds dirt and tends to hold onto any fuzzies from wiping cloths. A sanded surface cleans up easily.
I wasn't referring to self etching primers when I wrote "metal preps". I'm referring to the hand applied, out of the bottle, metal conditioners that a lot of the paint places have. Even these hand applied metal conditioners shouldn't be used under certain conditions, or at all, according to different paint manufacturer's recommendations for their epoxies. Running over any sandblasted body panels with a DA and some 80 grit is a great idea for the very reasons you stated. Of course, all the manufacturers assume you are going to have VERY CLEAN metal to spray over and using the DA as a follow up helps assure you that the metal is truly clean. Finally, the metal should be blown off with compressed air and cleaned well with a wax and grease remover prior to spraying the epoxy ...thus even more reason to clean and prep the metal well with a DA sander since the blasted metal will tear up the towels quickly when you try to wipe the metal with wax and grease remover as Walt mentions. Part of my postings are "splitting hairs" to some degree and you may be fine getting it back from a blaster, blowing it off, and shooting on some epoxy. Who knows??...only time will tell. However, if you have the time, the tools and the space to undertake these extra steps, you are eliminating some potential problems that MIGHT crop up later. Nobody can GUARANTEE the outcome of your paint job and disproving a negative is hard to do (IE--telling you to take steps to PREVENT a potential future problem that may or may not happen no matter what you do). Ultimately, that's your choice.
Patton, just so I'm clear, what you're trying to say is that, when it comes to paint, you should FOLLOW THE MANUFACTURER'S RECOMMENDATIONS? :laugh: A good example of why it's so important to read instructions: We all know that PrepSol is a good wax and grease remover. But did you know that it's not enough to just rub it all over the surface with a cloth? When the PrepSol evaporates, the wax and grease it picked up doesn't evaporate with it; it stays behind. If you read the instructions, the proper way to use it is to work on a small are at a time, wipe it on with a wet cloth, then -- while it's still wet -- wipe it off with a CLEAN cloth. Also, PrepSol is intended as much, if not more, for removing wax and grease BEFORE you DA all the old paint off than for cleaning bare metal. If you don't clean the old paint before sanding, your DA just spreads all that wax and grease around and embeds it in the bare metal.
