Primer Over Bare Sheet Metal

[AMX 390]

I am restoring a 1968 AMX.. I have completed all the metal work (welding in new patch panels floors made all rust repairs)and basically the car is rust free..I am at a point now where I am going to strip of the remaining paint so the car will be down to bare metal..Once I have done this I will have some minor plastic work to do..My question is what kind of primer should I use over all this bare metal.. Some say epoxy primer which I understand is really durable but can be difficult to work with or is there another primer system that I can use that will give me good results.. My concern with the epoxy is that if I do my plastic work over it I must do it within the seven day window before it cures..As a hobbyist I may not have the time available to get back to do the work within that seven day window. Is there a urethane system or something like that that will give my bare metal good protection and provide a good base for my topcoats that will be more forgiving when it comes time to do my plastic work.. I am an older guy and my body and paint experience goes back to the laquer and enamel days so all of todays methods are new to me so any advice you can provide will be greatly appreciated.

Thanks

[Steve g]

I am restoring a 1968 AMX.. I have completed all the metal work (welding in new patch panels floors made all rust repairs)and basically the car is rust free..I am at a point now where I am going to strip of the remaining paint so the car will be down to bare metal..Once I have done this I will have some minor plastic work to do..My question is what kind of primer should I use over all this bare metal.. Some say epoxy primer which I understand is really durable but can be difficult to work with or is there another primer system that I can use that will give me good results.. My concern with the epoxy is that if I do my plastic work over it I must do it within the seven day window before it cures..As a hobbyist I may not have the time available to get back to do the work within that seven day window. Is there a urethane system or something like that that will give my bare metal good protection and provide a good base for my topcoats that will be more forgiving when it comes time to do my plastic work.. I am an older guy and my body and paint experience goes back to the laquer and enamel days so all of todays methods are new to me so any advice you can provide will be greatly appreciated.

Thanks

The problem with most of the urethane primers is that they lack the superior adhesion to bare metal that epoxy has. More so than it's sealing properties, we use epoxy for it's adhesion qualities. It works like contact cement. You apply it, wait for the solvents to flash off then apply your next product, thereby "gluing" it to the bare metal. We use the urethane primers for their surfacing and sanding properties. They build up the surface and allow us to easily sand to a level surface. While there are some hybrids that claim to do both well, the major manufacturers, for the most part, seem to feel that is a compromise of one or the other. That's the position I take.

There's two different approaches I would consider. If you have a small amount of filler work, I would shoot the whole thing in epoxy (after stripping of course), followed by my high build within the epoxy's recoat window. I would then take my small grinder with some 40 or 80 to the areas I need to fill. Filler is best on bare metal according to first hand tests done by several of our members from time to time. It is acceptable over epoxy and will hold adequately, but holds even better on bare metal. Do my filler work, shoot the spots with epoxy and high build as I do them. Then proceed to block out the entire vehicle.

Alternately, you could do your filler work before you strip, then strip, epoxy and 2k urethane high build.

Steve g

[barthmonster]

Also where do you live ? Minnesota, then use epoxy for sure !! California or Arizona ? How about using Clausen Z-Chrome Rust Defender primer... Its a direct-to-metal polyester primer that's great for blocking (sprayable bondo) and in that climate I'm sure it would be fine...

[68Jcode]

Another variation on steve's suggestion would be to get the entire car in epoxy and 2K, then sand down to the Epoxy on areas where you need filler. If you go to the evercoat site in the FAQ section, it indicates their filler can be used over OEM paint sanded with 80-180 grit, so I would assume the same would hold for Epoxy.

Q. Can Evercoat fillers be applied over bare metal? Can they be applied over paint?
A. Our fillers are designed to work over bare, properly prepared substrates such as: steel, aluminum, galvanized, stainless steel, fiberglass, and SMC. Some people prefer applying an epoxy primer over bare substrates to enhance corrosion protection. Our products don’t need to be applied over an epoxy for corrosion protection as long as the bare surface area is clean and no surface rust or contamination is present. However, some auto manufacturers do require body technicians to coat the bare metal surface with an epoxy before applying fillers. If you are performing warranty work, you should consult the manufacturer of the automobile for the recommended procedure. Fillers and putties will normally work OK over properly sanded (80-180 grit) cured OEM paint. However, with so many different types of aftermarket paint available (lacquer, enamel, urethane, water-based). We recommend that all paint be removed where filler is to be applied.


I'm in a similar situation myself. My plan is to get all the low spots identified, sand to bare metal, epoxy, sand with 80 grit, fill, level out the filler, and finally strip the rest of the body, epoxy, 2K, block.

I used to be a filler direct to metal believer, but since I've got to stretch the filler part of the project out over such a long period, I prefer to have a coat of epoxy under it.

Hope this makes sense.

[AMX 390]

Thanks Guys for all the good info. I think what i will probably do is strip the car epoxy prime, do my plastic work and 2 k prime within the curing window..Looks like i will be burning a few vacation days..If i use this process how long should i wait after epoxy priming before doing my plastic work..After doing the plastic work should I recoat the plastic and surrounding area with epoxy or just coat with 2k. How much time do I have after the original epoxy prime do I have to 2 k prime (7 days ?)..

On another related subject.. At one time in its life this car had one of its rear quarters replaced..The body shop that did the work (probably back in th 70s) filled the seam between the roof and the quarter with body filler.. This filler is showing a little crack.. What i would like to do is remove all this filler and redo using a metal filled plastic. filler. Should I clean out this seam epoxy prime and then metal fill or clean out the seam metal fill and the epoxy prime.. Is epoxy primer compatable with the metal fill plastic.. Thanks Again

[Steve g]

Thanks Guys for all the good info. I think what i will probably do is strip the car epoxy prime, do my plastic work and 2 k prime within the curing window..Looks like i will be burning a few vacation days..If i use this process how long should i wait after epoxy priming before doing my plastic work..After doing the plastic work should I recoat the plastic and surrounding area with epoxy or just coat with 2k. How much time do I have after the original epoxy prime do I have to 2 k prime (7 days ?)..

On another related subject.. At one time in its life this car had one of its rear quarters replaced..The body shop that did the work (probably back in th 70s) filled the seam between the roof and the quarter with body filler.. This filler is showing a little crack.. What i would like to do is remove all this filler and redo using a metal filled plastic. filler. Should I clean out this seam epoxy prime and then metal fill or clean out the seam metal fill and the epoxy prime.. Is epoxy primer compatable with the metal fill plastic.. Thanks Again

I would advise against that plan. You will have all that epoxy exposed to the contaminants that you will create when you do your filler work as well as the usual hand prints and other air borne pollutants. You are placing the entire surface at increased risk in order to ensure you have epoxy under your filler, which has little to no benefit. You've now also set yourself a deadline. No matter how things go you have a date with that spray gun. Miss it and you've got a lot of sanding and wasted material. If you want the true benefit of the epoxy, if you miss the recoat window you have to sand everything, shoot another coat of epoxy then move on. For reasons outlined further down, I like my epoxy topped as soon as possible.
How long your recoat window is is specific to the product you use. My favourite epoxy, Omni's 170 has a 3 day recoat window. You would be safe to cover it with filler in about an hour. If I were doing it that way I would make sure I had some very coarse tooth under the epoxy, 24 or 40 grit, such that the epoxy did not fill it. Remember, when it comes to recoat window, the curing process starts immediately and the adhesion properties diminish until they are no longer adequate (end of recoat window). What that means is that adhesion is best earliest. I like to seal my filler work with epoxy before going on to my surfacer.

The filler cracking in the sail panel had nothing to do with it not being a metal filler. Clean it out and look for a poor mechanical join. Plastic is used there all the time and there is no benefit to using a metal filler.

Steve g

[AMX 390]

Steve.. I am a little confused..But that doesn't surprise me.. Anyway.. If I am understanding this correctly I should epoxy prime the whole car followed by the 2k..Then I can go back and scuff/ griind off (what grit) at my leisure the material that is in the areas that need plastic work... After the plastic work is done recoat these areas with both the epoxy and 2 k..How soon after applying the epoxy can the 2k be applied

[Steve g]

Steve.. I am a little confused..But that doesn't surprise me.. Anyway.. If I am understanding this correctly I should epoxy prime the whole car followed by the 2k..Then I can go back and scuff/ griind off (what grit) at my leisure the material that is in the areas that need plastic work... After the plastic work is done recoat these areas with both the epoxy and 2 k..How soon after applying the epoxy can the 2k be applied

Yes, that's exactly what I would do. You can take your little 4" grinder with a 40 or 80 grit disc and just hit the areas you're doing your filler work. One at a time,at your leisure. If the car is not exposed to the elements or high humidity and depending on the total timeframe and and number of repair areas you can just leave them sit in filler until they're all done then hit them all with your epoxy then with your 2k surfacer. If it's an extended time and/or there are many, prime when you're got 2 or 3 done. You generally will want/need more of your 2k surfacer over your repair areas than the surrounding untouched areas anyways. Check the tech sheets for your particular epoxy for recoat/flash times, but in most cases an hour is plenty of time for the epoxy to dry before recoating, assuming proper temps and good air movement. When shooting your epoxy on your repairs try to keep your epoxy confined to the metal you bared and the filler, avoiding the adjacent urethane if you can (controling all this with your gun. Don't mask anything because that makes ridges. Just pay attention to what you're hitting). Then cover it with with your urethane surfacer. This avoids running into the epoxy prematurely as you're blocking the urethane

Steve g

Edit: I realize I'm making these recommendations on the assumptions that your plastic repairs are small creases or door dings. If you have a larger repair area simply shoot around it when you're priming. If you want your epoxy under the filler, go over it with that and shoot around it with your 2k. Just wastes less material. Either way you want at some point to create a 40 - 80 grit tooth for your filler tho. Also, I would attend to the sail panel before stripping and priming. You may find that some welding is warranted and you want that out of the way before you start putting paint on things.

[88GT]

I had a 68 Javelin for my first ride. Id love to see pics

[AMX 390]

Continueing my my quest for information on modern auto body techniques my question now is regarding 2 k primer.. After blocking ,if a low spot is detected can a glasing or fiinishing putty be applied over the 2k in the low area and then reprimed with 2k..Or do you need to remove the 2k in the low area and apply the putty or a standard body filler and reprime

[Len]

Continueing my my quest for information on modern auto body techniques my question now is regarding 2 k primer.. After blocking ,if a low spot is detected can a glasing or fiinishing putty be applied over the 2k in the low area and then reprimed with 2k..Or do you need to remove the 2k in the low area and apply the putty or a standard body filler and reprime

Just scratch the low spot with a little 80 grit and press the filler into the scratches on your first pass then fill it up, let it harden and block it level then reprime with more 2K then guide coat and block sand with some 400/600.

[88GT]

dont use standard filler for that. Use either glazing putty or a finishing filler like rage extreme or marson platinum

[AMX 390]

I want to thank everyone for all the good information and patience when answering all of my dumb questions..I now have a better handle on what I need to do to get my car ready for paint..I see the link to Lens painting DVD and will be purchasing it as soon as I finish with this response..Hopefully after viewing the DVD I will be able to ask some intelligent questioins in the future..This is a terrific site and is a very useful tool..

Thanks Again
Joe