I am going to strip the entire care to bare metal for paint. Should I use etch primer or epoxy primer on the bare metal? I've been told the etch primers and filler don't get along well. I was planning on stripping the care to bare metal, priming then going back and restripping the areas that need filler and doing the mud work. Can filler be applied over Epoxy primer? or will it stick better to bare metal? I want to do this once and do it right. Thankx, Todd
On fresh new metal etch primer is my preference. Consider that it does what the name implies. Epoxy is also a good choice for durability and UV protection (something that gets forgotten now and then). Most fillers are compatable with most epoxy coatings but I'd advise you to get a tech sheet on what ever product you intend to use to be certain. One time saver to epoxy is that it remains ready for re-coat for several days...3 to 7 depending on formulation. This can go a long way towards getting a good clean finish. I personally prefer to strip after all metal and welding work is done. By that I mean having parts professionally stripped by burn/chemical or electrolytic process. That way any contaminants from the weld and repair process also get cleaned better than by hand. Most polyester primers like Slick Sand and Featherfill do not adhere to either epoxy or etch primers. I hope this was helpful. Good luck with your project.
When I strip to bare metal, I like to do all the metalwork and welding first. Then I spray HOK Direct to Metal KD2000 Epoxy Primer. That stuff is the best by far in adhering to bare metal and alows filler over the top with no problem. After I do my filler work, I seal it up in HOK KO Seal II. Once thats done, a quick wetsand and its ready for final paint.
I use a cheap etch primer from Napa after the car is stripped and blasted. When its time to go to putty I take a fresh 36 grit disk on an air grinder and lightly scuff the **** out of the metal, removing the primer in the process to the panel that is to be filled. This gives the metal the "tooth" needed for the putty to really bond good. I wouldn't ever put putty over primer.
I always put filler directly onto metal first. My '63 truck has HOK epoxy (KP2CF-I think) primer sprayed on top of that. Haven't had any rust/bubbling up issues yet, and I sprayed this 3 yrs ago.
PPG DP...then go back and sand it off where I put filler. Then I start with polyester primers, then some K-36, then DP again before basecoat.
good epoxy primer for bare metal or on top of filler.. www.southernpolyurethanes.com this is the best i think and cheaper than most
We used to do that also Roach. But if your going to sand it off anyways, might as well use a cheaper product like the napa stuff we use. I think its Martin Senior brand. Its a lot like PPG's DX 171. Also, DPing after your Primer Surfacer is a little old school. We have good luck using K 38 as a Primer Surfacer (a lot less shrinkage than K36, and it's a lot nicer to sand) then if you want to seal before paint use the K 36 mixed as a sealer.
I've been using Martin Senour products for 25 years and have attended their refinish training centers. Back then the hot product was a vinyl wash primer over the bare metal for adhesion and corrosion protection. Products evolved and etching primers replaced the wash primer. I think Napa's Crossfire etch primer is a good primer for the money. Napa Martin Senour has always taught that body fillers should be applied to clean properly prepared bare metal. That's the way I've always done it and then primers go over top of body work and filler. If I had to prime a complete bare metal surface that was stripped prior to body work, I'd sand off the primer when ready to apply filler and then reapply the etch filler over any remaining bare metal. It'll go over filler no problem but offers no corrosion protection over the filler. I think the big reason people favor the epoxy under the filler is that the entire metal area is coated even under the filler. No need to break the initial film again. I can't say that this is a bad idea. It does work. I've used 2k primers over top of the etching primers when I've needed some film build to block sand but if you really need to go with a polyester primer filler like slick sand over lots of body work you may be better off with the epoxy primer instead. Epoxy primers have been around for a good while and I think their initial use was intended for the industrial coatings more so than automotive, but along the line they became commonly used on cars. Seems to me like the PPG guys favor the epoxy over bare metal and fillers applied right over top of the epoxy. As far as pros and cons of which is better- both ways work. Follow manufacturer's instructions and best to stick with all products from one brand. Hope this helps and have fun!
I like to do the major metal work first, then strip to bare metal, prime with an epoxy primer (DuPont or PPG DP), then I sand it where it needs filler with 50 or 80 grit. In California where I live, they kept making the primer/surfacers I was used to illegal over and over, so lately I've been using Evercoat Feather Fill G2 (generation II), which is a polyester primer. I spray it through a 1.4mm tip which makes it lay down pretty flat and not too thick and it sands about as easy as something like PPG K-36. I like that Feather Fill G2 stuff and it seems to stick well to sanded epoxy primer. If the parts don't need any filler, you can go right from epoxy primer to the Feather Fill G2 and you have a couple of days window to shoot it over the epoxy without sanding if you don't feel like sanding the epoxy primer, but I sand it anyway. I don't think many body shops use epoxy primer over bare steel mainly because it's expensive. But I think it's standard practice for restorers and people who really want the paintjob to last as long as possible. I only paint cars or parts about every few years, so it doesn't kill me to pay a little more for epoxy primer. The shelf life of epoxy primers seems to be longer too than other primers. I also like how you can keep the steel protected while you take your time doing filler work. I get the steel as straight as possible before the epoxy primer so the filler is only maybe 1/16" thick at the most though. I don't know how it would work thicker than that, but it works great for thinner patches of filler. Epoxy primer is really tough stuff. I've never had a problem with filler over sanded epoxy primer. If you use a dark grey epoxy primer, it turns lighter colored when you start to sand it, so low spots become really obvious when the sandpaper misses them.
You are correct sir. Ive started using the Shop Line brand epoxy lately. Cant remember the numbers right off hand but I believe it works just as well and lasts just as long as DP. K 38 is an excellent product, but if Ive used a polyester primer before-hand, ive done all my blocking sessions with it. And just need a good surfacer to wetsand on. I know its a bit old school but unless I want the surface to be gray for my base, I'll use an appropriate color of DP or even the Shop Line. It all depends on what base color Im using. Also, as stated before, I was taught in a restoration and collision repair shop so thats where I get my take on epoxy over the entire car before anything else.
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