TheSamba.com :: View topic

Tue Feb 25, 2003 5:52 pm

OK, I am down to bare metal with just finishing prep and "all metal" filler work to be done on welds, un-reachable small dings and imperfections. I am taking the vehicle to a pro paint booth for dupont base/clear paintjob but I am going to do priming/surfacing/sanding (if needed) my self.

From what I have seen, I can use a surfacer to fill small scratches, imperfections, etc. Those need to be block sanded down prior to color coat. I also see that Dupont (I want to use only dupont prime products to stay with same "system" as paint) makes a product called DTM epoxy primer/sealer that does not need to be sanded prior to color coat. The obvious difference would be that my prep work would need to be practically flawless in order to go that route or scratches and imperfections that would be covered by the high-build surfacer would be exposed and show up in my final paint job.
1)What are your suggestions in this process?
2)What grit of paper would I have to use to get the filler and bare metal smooth enough to go with a non-sanding primer/sealer that only gets two coats?
3) What about etching primer? The prep process I used is as follows: Plastic media blasted paint off. any surface rust was wire wheeled on a drill or grinder till all metal was shiny and then "metal prepped" with POR-15's product to convert any microscopic rust particles missed by blasting and wire wheel. Then the entire surface hand sanded to get metal super clean and then wiped down with metal cleaning solvent made for paint shops. All the time kept in a heated garage? Do I need to use an etching primer or can I go straight to it with a primer/sealer or high-build surfacer (again..all dupont).

Your help is appreciated.

Doug

Wed Feb 26, 2003 11:55 am

If Dupont makes an etching primer, use it. It gives the filler/sealer something to adhere to that is itself adhereing to the metal. I don't know anything about the primer that would not need to be sanded, but I would be a bit skeptical about how the color coat would lay, I don't know? If you went that route I would think you would probably want to go with a 220 grit or something that if fairly fine, but not so fine that there is no etching for the primer? Again, I have no experience with this, just making educated guesses. If your body work is pretty good, you might be able to get away with spraying the sealer, relativly think, then wet sanding that with 600 before the color coat and skipping the whole filler step. I would definitly go with some sort of a sealing primer as the last step before paint though. Good luck!

Wed Feb 26, 2003 3:38 pm

I am having trouble finding usage recommendation for Dupont and other manufacturing companies products. I have pretty much decided to go as below. Does this sound like a sound way to approach the pre-paint process?
1) after preping metal, spray an etching primer on bare matal and filler.
2) Then spray a high build primer/surfacer.
3) Sand it down smooth as per manuf. instructions.
4) spray again with primer/sealer for good paint adhesion and to stop color base coat from "soaking" into the sanded primer/surfacer.

Do I need a 5th step that would include sanding the top coat of primer/sealer again? seems like mucho sanding to sand the primer more than once. Hell, I still got to color sand and polish after it comes back from painter still. But I do want a quality looking job and if I need to spend yet another weekend sanding....then so be it.

Thanks again for your time and replies.

Doug

Thu Feb 27, 2003 5:16 pm

Don't spray the etching primer over any filler, it will eat through the filler and it will flake off the metal and you will be in big, big trouble. A little overspray is ok, but keep the etching primer only on metal!!!! Like I said before, if your body work is good, you should simply spray the sealer over the etching primer, wet sand that with 600 and paint it. You really, really need to wet sand the final coat of primer, especially on large surface areas to get the paint to really lay flat and smooth. If you want to go the route you outlined, that would be fine, but add a number 5 being wet sand with 600 prior to paint. The paint will not soak into the primer so much that you will have to keep spraying and spraying. I would call the place you got your paint at and ask them what the manuf. recommendations are if you are unsure. Have fun!

Thu Feb 27, 2003 7:27 pm

I would add, POR-15 is NOT intended as a sublayer for finish painted body panels. It is best used as a stand-alone finish for underbody and interior panels such as the pan, tunnel, torsion beams, etc.

Sun Mar 02, 2003 8:20 am

If you choose to use a sealer over your sanded primer coat, keep in mind that most sealers are intended to be used "wet-on-wet" w/ no sanding before applying the colorcoat. Instead of a mechanical bond ( I.e. sanding/scuffing) these sealers use a chemical bond.For this reason, timing is very important. There is a window in which you must adhere to for the sealer and basecoat to crosslink. Anytime you go past this window you must go back to the mechanical bond idea and re-scuff or sand. I like to think of it in two steps. The "priming/prepping" stage of a paintjob ends once the build primer is sanded out. The "painting" stage actually starts when you spray your sealer.The sealer I use can be topcoated after 30 minutes, but within 4 hours.You might want to just get the vehicle primed and sanded yourself and let the painter apply the sealer.Maybe ask him what he prefers/suggests?
Also, I am very skeptical about etch priming , sanding w/ 600 ,and then going straight to sealer as Ryan suggested. You need a build primer to smooth out the bodywork and take care of any sand scratches and imperfections.
Good luck! Feel free to email if you need any clarifications, Jason

Mon Mar 03, 2003 11:24 am

Sorry if you misunderstood what I said. With the product I used you have to spray the etching primer, then spray some other primer, building or sealer, over it before it is actually dry. Etching primer does not seal the metal from moisture and if you don't spray something over it right away you can trap moisture under the primer. I meant to spray the etching, sealer or filler, sand, spray sealer if you haven't, sand again, then paint. I think it depends on the brand of paint you use as to if you spray the color on the sealer when it is still wet, ask the supplier or body shop. Spies products use the same vario-surfacer for the sealer and build primer, just mixed differently. I'm speaking from my experience and have friends who paint for a living and agree with the approach I took. I'm not going to bad mouth Jason, all I'm saying is do your homework on the product you choose, don't rely on me or anyone else, this is more informational and just something to get you started.

Mon Mar 03, 2003 4:18 pm

Thanks guys.

Big help. I have been doing lots of reading since I started the posts and you are both dead on. There is some personal preferences and product related options. I have kind of decided on Duponts DTM (direct to metal) epoxy instead of etch primer for first coat. I am working on a rust free substrate with proper sanding grit after proper metal cleaner wipe downs. That way I dont have to worry about masking off filler where I feathered out my replacement panel welds. Then going to high-build and sand. There are several dupont high-builds primers that claim excelent topcoat holdout. I know a sealer is better and recommended. How do you guys feel about that?
Thanks again

Doug