Filler over old epoxy primer

S

ssanto

I had the car blasted and then I sprayed it with epoxy primer about 18 months ago. I've been driving it maybe once a week since then.

Now I'm going to come back to it and finish up the metal work.

Some questions...

1) Some of the panels don't need any metal work. Just a skim coat of filler will get it where I need it. Can I simply scuff the old epoxy and put body filler over it? Or do I need to re-spray it with epoxy? If so, can I thin it?


2) Some of the panels need more significant metal work. I'll do the metal work with the old primer on it. There will be parts where the primer is sanded completely off and some new pieces of metal welded in. Then I'll spray the whole panel with epoxy. And then do my filler work. And then hit the whole panel with high build primer and block it out. This process may take weeks. What is the maximum amount of time I can wait from when I shoot the epoxy to when I shoot high build primer?
 
I ask a similar question here a while back. If the epoxy has been in the sun for any length of time, it needs to be sanded and re applied prior to continuing. I believe the tech sheet states their is a 7 day recoat window on the epoxy. If left inside, I believe that window can be stretched and HB be applied over scuffed epoxy..
 
So many variables here, yes you could 180 by hand and apply filler but to error on the safe side, I would 180 and put another coat of epoxy on just because of the amount of time it has set.
 
Barry said:
So many variables here, yes you could 180 by hand and apply filler but to error on the safe side, I would 180 and put another coat of epoxy on just because of the amount of time it has set.
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This is exactly what I've done in the past and never had a problem. Two projects I've been on for several years I've done this very thing when things got delayed or sidetracked. 180 and new epoxy then filler in next few days.
 
A follow up question...

I've been reading about reducing SPI epoxy primer to use it as a sealer. Why would I do this? When is it appropriate?

Here is my plan:

0. Current state - car is completely in SPI epoxy primer from a year ago and needs metalwork/bodywork
1. Thoroughly clean
2. Metalwork - hammer/dolly, cut and weld patches in, strip paint where necessary
3. Scuff the panel with 180 grit (scuffing the rest of the epoxy primer that is still on the panel)
4. Shoot with epoxy primer
5. Filler work - rage gold first, then glaze/skim coat
6. Shoot with high build primer
7. Block
8. Let it sit (indoors) for a number of weeks while I do the other panels
9. Final paint

Is there any point in there where I should do a sealer coat?

Does anything need to go over the high build primer before basecoat?

Thanks!
 
Besides the function of sealing and providing a uniform surface, the thin coat of epoxy just before paint is an extra insurance policy providing extra adhesion between layers, which will reduce things like future rock chipping.
 
I suppose if my blocking breaks through the high build primer into the filler or even the metal, then I'd need another coat before shooting the base. However, the epoxy primer I've already got is black and I'm going to want to shoot a grey down before my red base. So I'll be needing to purchase materials for that sealer coat.

For the sealer layer, any pros/cons between choosing to use the SPI 2k sealer vs the 2k primer? Why would one choose the sealer over the primer if both could be used as a sealer coat?
 
ssanto said:
I suppose if my blocking breaks through the high build primer into the filler or even the metal, then I'd need another coat before shooting the base. However, the epoxy primer I've already got is black and I'm going to want to shoot a grey down before my red base. So I'll be needing to purchase materials for that sealer coat.

For the sealer layer, any pros/cons between choosing to use the SPI 2k sealer vs the 2k primer? Why would one choose the sealer over the primer if both could be used as a sealer coat?
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The 2K primer is not meant to be used as a sealer.

Did you mean the Epoxy primer used as a sealer vs the 2K sealer?
 
OK... let me see if I've got this straight...

- After blocking, I'm going to have some sand-through areas and should to another coat over the whole thing before bodywork
- I could use a coat of primer for this. Either high-build or 2K. And that would give me the consistent layer I need, but would not provide me with sealer properties.
- I could use epoxy primer or reduced epoxy primer. This gives me the consistent layer as well as sealer properties
- I could use the 2K sealer. This gives me the consistent layer as well as sealer properties



Questions (sorry if this is repeating my other questions):

What is the advantage of using a sealer before the basecoat rather than just another layer of prime? Does the sealer provide better adhesion? Is there really a need to seal the filler/primer if I've got epoxy under it and basecoat/clearcoat on top of it?


What is the advantages of using the reduced epoxy primer over the 2K sealer (or vice versa)? Does one lay down differently and have different requirements for sanding before basecoat? Or is it mostly a matter of just using whatever I have on hand?
 
ssanto said:
OK... let me see if I've got this straight...

- After blocking, I'm going to have some sand-through areas and should to another coat over the whole thing before bodywork
- I could use a coat of primer for this. Either high-build or 2K. And that would give me the consistent layer I need, but would not provide me with sealer properties.
- I could use epoxy primer or reduced epoxy primer. This gives me the consistent layer as well as sealer properties
- I could use the 2K sealer. This gives me the consistent layer as well as sealer properties



Questions (sorry if this is repeating my other questions):

What is the advantage of using a sealer before the basecoat rather than just another layer of prime? Does the sealer provide better adhesion? Is there really a need to seal the filler/primer if I've got epoxy under it and basecoat/clearcoat on top of it?


What is the advantages of using the reduced epoxy primer over the 2K sealer (or vice versa)? Does one lay down differently and have different requirements for sanding before basecoat? Or is it mostly a matter of just using whatever I have on hand?
Click to expand...

The 2K sealer is used more in a collision environment where you need speed, lays down very smooth and you can denib-scuff in 15-20 minutes very easy. It will increase adhesion over just shooting basecoat over the 2K primer.

The epoxy as a sealer I believe it will give you better adhesion, it is a bit trickier to spray compared to the 2K sealer, and if you need to sand-denib you may have to wait longer, say about an hour depending on how much you reduced it and how you sprayed it.

I have sanded reduced epoxy (1:1:1) in as little as 15-20 minutes by spraying solvent W&G remover on a piece of sandpaper, usually 600-800 grit then going gently over the surface and wiping it off. You just use the W&G as a lubricant.

Hope this helps you, I've never been good at explaining things lol
 
To back up a little bit, there is always better & best with products, which may make a bigger difference years down the road than now. There is also dry time of different products , which matter more in lets say the collision business, rather than a best of the best restoration.
If you hit filler on a sand through, then 2K over it before another sanding is fine. You may choose just to spray just a little past the offending sand through rather than recoat the entire part depending on the sand through & the intended quality level of the job. How many times you spray & sand is up to you & the desired job level.
For a small sand through to metal, you could get away with 2k, but epoxy to the metal is always safer for long term, particularly for corrosion resistance.. Also epoxy can be used as a sanding filler primer . Some just use epoxy & not 2k. tougher in long run, but slower to dry & build up thickness. So in terms of what you have on hand, you could use up your black epoxy in place of 2k.

In terms of sealer, time to order materials since black epoxy isn't what you want & 2k primer isn't intended as a sealer. For a color like black, sealer may not be as important from a color consistency standpoint as other colors , but for red it definitely is. Intended sealer products also have other properties, such as preventing future bleed through. As I stated before, for max adhesion , epoxy done in the correct time frames is best.. Reread info here such as perfect paint job. On what I have left of my personal vehicle black DuPont repaint from 1999, the DuPont sealer coat has been the weak spot in chip resistance. I think my long term example explains the difference in products. Most bad ass glues are epoxy based, right?
Hope this helps your understanding.... If you still don't have an understanding something on a subject here, always best to just stick with consistant advice given here, rather than trying to do your own thing, which you could regret sooner or later.
PS, I was typing this while Jorge commented, not meaning to re-repeat info.
 
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This is exactly the detail I was looking for. Thank you very much!
 
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