Order of things
I have read a lot of threads as to what material to lay first, everyone's opinions on etch vs epoxy etc. I think I understand for the most part. The question I have is... are there general rules as to what materials can be laid on top of previous materials? For example, I read that some preferr to use epoxy to seal the bare metal... Ok so now that you have sealed with epoxy, is it ok to lay a 2k urethane build primer or should you use a polyester filler? I mean is it a no no to put urethane on top of epoxy? For another example, I read another post where someone stated to shoot bare metal with etch, then follow it up with epoxy, then follow with a 2k build primer, block and base etc... why would you follow the etch with epoxy, or if you use etch is urethane ok on top of it? what about polyester? Sorry, I'm just confused...
Etching primers were designed for increased adhesion back when lacquer primer was the only surfacer available. They are still in use and offer excellent adhesion to bare steel. The only drawbacks are that they are a 1K product that is forever soluable, if you wet the surface of dried etch primer with solvent it will wash right off. Etch primers can be coated with epoxy and or urethane surfacers. Some newer polyester primers are claimed to be compatible with self etch primers but when I tested this it showed a very slow cure and definitely softened the etch primer underneath.
The only time I use a self etching primer or etching wash primer is on bare metal surfaces that cannot be prepped properly for epoxy primer.
IMO your best bare metal primer is epoxy if applied over a sanded and clean surface. Epoxy needs texture for proper adhesion and most manufacturers suggest sanding the bare steel with 80-180 grit. A sandblasted texture is also ideal. Epoxy offers excellent adhesion and the best durability in a 2k product that is not soluable after full cure. Any polyester or urethane product can be applied over epoxy.
1. sand and clean your bare metal surfaces
2. apply two coats of epoxy primer and let dry overnight
3. do any polyester filler work over the epoxy, if the epoxy is over three days old scuff with a red scotchbrite prior to filler application
4. apply two more coats of epoxy to seal your filler work and also any bare metal cut throughs
5. apply the surfacer of your choice either polyester or urethane
6. block sand the surfacer
7. some surfacers provide an ideal surface for paint while others are absorbent and will need to be sealed.
There's many steps to doing this right, more time than the average body shop will spend. Most will just mud, prime, and paint. JMO's Bob
Lets make it simple, if you are going to use todays products, you are going to use EPOXY, 2K PRIMER, POLYESTER PRIMER, BASE COAT, CLEAR COAT.
The epoxy is great for plastics, bumpers and bare metal, you can cover the epoxy with body filler for repairs.. You can then follow that with 2k to cover your repair area's... Then all you have left is bc/cc...
Too many people will not let go of something they have gotten used to or someone told them something that is not right, but they paint well.. etc....
The poly primer is like spreading metal glaze over a panel, except it is sprayable ( nice )...
For most repairs when you cover metal use epoxy. You dont have to go over it with 2k if everything is tip top.. You can let it flash and bc/cc.. For most they will cover with 2k to check bodywork etc...
Hope this helps some... It really is not as hard as many make it bro
Thanks for replying, being that I have had my car for approx. 20 yrs, I have been able to start multiple times just to be shelved again and again... I'm bound and determined to get there. So the things I read and learn, I try and apply when I can. So I got the basics (I get to practice on things, projects other than my car) I just don't get to do it enough to know what you guy's know. I have read almost all of the articles in the knowledge base for body/exterior. there is a real good article by Martinsr on the different products and their definition as well as what they are used for. I just could not find the compatibility between the different medias (plastic to urethane to epoxy etc.) thanks for straightening that up...
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