Issues with epoxy bond under filler

If you don't know what you are doing then don't do it. You have been told what the problem is, stop looking for another answer and quite using your technique, listen to and follow what you are being told and what you are doing wrong and make the necessary corrections.

IMO anything "All Metal", "Metal 2 Metal" etc, etc is just stupid. You want problems then go ahead and keep using it it has no more durability then Duraglass it can bubble like anything else, I have seen it first hand. You will never see it used in any of my jobs or anywhere in my shop.

Baking soda neutralizes acid water alone will not.
 
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I'm not looking for another answer, nor do I have any specific "technique"...I'm simply trying to figure this out without jumping to conclusions. I may not be a pro body man, but I work in a very technical field and I don't jump to conclusions when troubleshooting, I want answers based on what results I see and what is reasonable, not on what the last guys problem was.

Unless I have a comprehension problem, my understanding about Barry's suggested adhesion test was that if there was no acid film, the filler should just chip away and not pull off the primer. As I explained, the filler only chipped and would not come loose in 9 out of 11 tests.

Perhaps I did not explain well enough, but the 2 locations where the filler came off were spots that the filler had a lot of overhang and I was able to get the screwdriver 1/3 of the way under them. It was a big screwdriver with a 1/2" wide blade. When I tried to pop them off, they did not give at all until I applied a LOT of pressure, so much so that when one let go I banged up my hand pretty good. They did not just pop off.

In both of those cases, the failure was between the filler and primer, not the primer and substrate below. There was no marking or damage to the primer in these spots except for yellow staining from the filler.

The primer was soft under these areas. I am interpreting that to be because of the filler solvents but do not have enough experience to know for sure. If the primer was being affected by an acid film and not because of solvents in the filler, why would the one area be soft when the substrate below was a previous layer of sound epoxy primer?

I'm looking for a constructive technical discussion here, nothing more. At the end of the day, I am making the decision on how to proceed and whatever I decide will be my problem if I am wrong, nobody else's.
 
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I don't think you'll get a pat on the back and everything is OK around here. Most of us here would eat the job, re-strip, neutralize, and move forward even if the chance for a problem is slim.
A lot of us have been there and you know theres a chance for a problem down the road. Products are too expensive and so is labor. Your at a better stage to redo than after it's painted.

We used to use Dupon Metal prep but I haven't touched it over 12 years and haven't have a single problem. I'd never use that stuff or anything like it every again.
 
I think everyone could cool off a touch. Not trying to fuel a fire or anything like that, but it really seems like he understands that his prep could have caused the problem and he just wants a technical discussion on the how and why.

I had this same problem when I first came on this site. I had been using POR-15 before I realized what a "sin" it was. However, I didn't want to just take everyone's word for it, I wanted to know the reason behind the suggestions. I took a decent beating of "just do it this way) but eventually I did get a good technical reason.

If someone knows the answers to his questions, jump in. Otherwise, maybe just follow the golden rule!
 
While I agree that looking for a detailed analysis on why things don't work is perfectly fine. I also understand that there are Professionals on here with decades of experience who can tell you what works or doesn't by wisdom gained through trial and error. They may not be able to explain the incompatibility of the chemicals or underlying reaction that causes one thing to work and another to fail. However their experiences, wisdom and advice can be taken at face value especially when you have more than a few of them telling you the same thing.
Just my 2 cents and worth exactly what you paid for it.
 
Agreed, but he has only been a member since Tuesday and may not know who to trust or who is a seasoned pro. There is also people on this forum (1 sticks out especially) who give out advice on a lot of threads, but is not too experienced and often gives poor advice that is sometimes corrected, sometimes not. So unless he has been lurking for quite a while, I would say his want for reasoning instead of "just do this" is a cautious approach that should be followed anytime someone is new at a forum.
 
"So unless he has been lurking for quite a while, I would say his want for reasoning instead of "just do this" is a cautious approach that should be followed anytime someone is new at a forum."

Exactly right, I just got here and don't know anyone or anything about the forum except that Barry owns the place and makes a good product. I'm not about to start grinding everything off my car without understanding why I need to do that and being convinced that it is necessary. I am not trying to be hard headed here, but it seems that the second I said "metal conditioner", there was no further discussion other than "just start over". I respect other opinions and experience, but unless an old pro is standing in my garage seeing what I am seeing, I have to make the call and describing what is going on is not always easy with text.

Remember, my issue was soft primer under the filler, not adhesion problems with primer on the metal. The only specific advice that resembled a test was from Barry, and if the filler had popped off with primer attached in even one spot, I would be the first to say I am getting out the sander and starting over. That did not happen, which is why I am still asking questions.

For what its worth, the 2 areas that I did break the filler off that had soft primer underneath, are hard again and I cannot scrape the primer off at all. Does that indicate anything?

In the event that I do put on my big boy pants and start over, after getting down to bare metal what would I use to wipe the bare metal, (process, mixture ratio, etc.) before priming again? Someone mentioned baking soda, I assume leaving a residue from a base isn't much help either so a thorough rinsing is needed. I would like to hear specifics of how others have dealt with that.

Thanks again, I do appreciate the discussion.
 
If I understand this correctly, you used RM epoxy over RM metal conditioner and had this problem---so why not call the RM tech line to find out what happened with their products. These metal conditioners are not all the same, phosphoric acid is just the main ingredient, so they should be able to tell you if your procedure and flash times were acceptable. Since you insist on knowing what went wrong, I would want to make sure to tell them the correct flash times you used.

TDS says
Apply thin coat
Allow R-M 801 to remain on the metal for a minute or longer. Do not let dry.
While still wet, wipe the Metal Conditioner off with a clean dry cloth.


Things NOT to DO:
• Do not use on any areas where 834 Zip Zinc Phosphate Primer will be used.
• Do not use without reducing with water.
• Do not let 801 Metal Conditioner dry on substrate before wiping off.
 
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mrennie said:
"So unless he has been lurking for quite a while, I would say his want for reasoning instead of "just do this" is a cautious approach that should be followed anytime someone is new at a forum."

Exactly right, I just got here and don't know anyone or anything about the forum except that Barry owns the place and makes a good product. I'm not about to start grinding everything off my car without understanding why I need to do that and being convinced that it is necessary. I am not trying to be hard headed here, but it seems that the second I said "metal conditioner", there was no further discussion other than "just start over". I respect other opinions and experience, but unless an old pro is standing in my garage seeing what I am seeing, I have to make the call and describing what is going on is not always easy with text.

Remember, my issue was soft primer under the filler, not adhesion problems with primer on the metal. The only specific advice that resembled a test was from Barry, and if the filler had popped off with primer attached in even one spot, I would be the first to say I am getting out the sander and starting over. That did not happen, which is why I am still asking questions.

For what its worth, the 2 areas that I did break the filler off that had soft primer underneath, are hard again and I cannot scrape the primer off at all. Does that indicate anything?

In the event that I do put on my big boy pants and start over, after getting down to bare metal what would I use to wipe the bare metal, (process, mixture ratio, etc.) before priming again? Someone mentioned baking soda, I assume leaving a residue from a base isn't much help either so a thorough rinsing is needed. I would like to hear specifics of how others have dealt with that.

Thanks again, I do appreciate the discussion.
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Once you go to bare metal with 80 grit DA all you need to do is clean with SPI 700-1 waterborne W&G remover, then for good measure follow it with SPI 710-1 solvent W&G and you're good for primer. Use clean air to blow the panels for a few minutes to make sure all the W&G is dry and out of the metal pores and then start spraying.

I don't understand why people insist in any type of metal treatments and this and that, once you have fresh bare metal just clean it, epoxy it and call it a day.
 
Only reason I would ever use a acid based metal conditioner would be for deeply pitted rust that I for some reason couldn't media blast. Which for me is next to never. I think I've used it like 2 times in 25 years. Like Jorge said no reason to do it with anything that will clean up with 80 grit. If it doesn't clean up then media blast it.
 
Chris_Hamilton said:
You are still clinging to Old Tech. Epoxy is New Tech. It's been said a thousand times but here it goes, If you are going to apply an Epoxy primer over something that you used a phosphoric acid treatment on you need to neutralize the acid. Hence the reason for water. Epoxy will not bond with an acid film which is what you have left after using a phosphoric acid based metal treatment. The bond epoxy has with clean bare steel is far superior to anything you can get with an acid based etch primer or using a phosphoric acid based metal treatment. I don't care what industry you are talking about epoxy will not bond properly over an acid film.
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https://www.bmwusfactory.com/manufacturing/production-process/paint-shop/

This is the brand new state of the art spec for painting BMW's, starting with, you guessed it, a PHOSPHATE coating, followed by E coating for the primer stage, then right to base coat.

Maybe you are stuck with the old tech. All we get told around here is to strip e coat, when that is the choice for manufacturers with brand new metals.

You CAN use a phosphate treatment and not scrub it all off with scotchbrite or 80 grit. If you are using it so concentrated that you are leaving a white film or sticky residue, you are simply using it wrong. It gets to the point, like I wrote, if you do not believe or trust it that you want to take it all off, then why use it at all?
 
Not trying to get a fight started. :) All I know is that every OEM now recommends that epoxy be used on bare metal and under body filler. Mercedes has recommended it since the early 90's. We are refinishers so what the OEM's do in the manufacturing stage is not reproducible in the body shop. And I was speaking to Epoxy which according to everything I have ever read and backed up by Barry here does not bond well with an acid film.
 
Comparing a tightly controlled process performed in a factory to what can be achieved in a home garage is not a wise plan. The kind of metal treatments used under OE coating are fully neutralized and leave only iron or zinc phosphate residue, but in a less controlled environment, an acid residue is highly likely.

So it's not like you couldn't use an acid treatment if everything went perfectly, but the easy assumption to make (since the old timers on here have seen it a thousand times) is that the process won't be completed to perfection. As far as most of us (and SPI) is concerned, acid treatments are a high risk and low reward proposition, since an 80 grit scratch or abrasive media profile plus proper cleaning provide excellent adhesion without excess complication and room for error. There's absolutely no reason for a hobbyist to put their entire job at risk by performing unnecessary and risky procedures.

@mrennie, you'll just have to use your best judgement to decide whether the epoxy is adhering to the metal well enough now or not. But I strongly suggest that no matter what you decide on the existing work, that moving forward you will "adhere" to the SPI recommended procedure, which has already been outlined previously in this thread.
 
Just noticed I don't see it here on the new updated forum, but the epoxy torture test video that used to be at the top of the forums page first showed epoxy over acid, which failed & other tests including body fillers held up to torture. Although it was an amature home video, It showed the result of what not to do.
Original poster, since you've had another week of drying time since first posting, I'd try an adhesion test of pressing on duct tape in spots & peeling it off. If it pulls off epoxy now, time to just suck it up & start over now or regret it later.
 
"@mrennie, you'll just have to use your best judgement to decide whether the epoxy is adhering to the metal well enough now or not."

I've pretty much resigned myself to stripping the primer/filler I already did and starting over. Not because I could see a definitive problem, but because I have put $$$$$ into this thing and since I cannot be 100% sure there isn't going to be a problem area down the road, it seems to be the reasonable thing to do. I really think the soft primer under the filler is due to the filler solvents, because I cannot get the primer to come off anywhere, even using a blow gun or scraper. If someone had said, "yeah, seen that lots of times, primer soft under filler but no loss of adhesion when cured" I would proceed differently. So, I will have to strip both doors, roof, and one quarter, as those were areas with surface rust that I used the RM metal conditioner on.

My plan is to strip back to bare metal, re-wet with metal conditioner and scrub pad, then rinse with clean water and dry off, then wipe down with 700 W&G remover, then DA again with 80 grit, then wipe again with 700 W&G remover, then wait 4-5 hours and epoxy prime. If that doesn't do the trick I don't know what else to do.

I have the dehumidifier cranked up and humidity in garage is 30% so hoping for no rusting between the time I rinse and time I prime.
 
Just remember, the metal conditioner must be wet when neutralized , or you will have problems.
I just don't get why you want to risk it with that stuff???
Says on tech sheet never use under Zinc Phosphate and the epoxy is maxed out with it, like ANY good epoxy or DTM would be.
 
"Just remember, the metal conditioner must be wet when neutralized , or you will have problems."

Understood, thanks.

"Says on tech sheet never use under Zinc Phosphate and the epoxy is maxed out with it, like ANY good epoxy or DTM would be."

!!!!!

Thank you for explaining that, it gives me piece of mind that stripping and starting over is the right thing to do!! I did not know epoxy contained Zinc Phosphate, and had I understood that I would not have belabored the situation with so many questions trying to understand if I was going to have a problem or not.

A case of beer and some loud AC/DC on New Year's day should get me through the worst part of this...... :)
 
thank you for your decision to strip it. The end result would make SPI look bad and it is far from it, also don't use metal 2 metal crap either just another risk that can play havic for no good reason.

On a side note E-coat is not Epoxy so forget the process of manufactures, you can't compare the 2 processes.
 
Just so there is a clear understanding here and not to mislead.

If an acid is neutralized properly then all is well and the zinc phosphate no longer applies.
 
DATEC said:
...On a side note E-coat is not Epoxy so forget the process of manufactures, you can't compare the 2 processes.
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Actually, many e-coats ARE epoxies, here is but one example:

http://www.ppgecoat.com/getmedia/b476149d-dd14-4df4-ac35-5e280872d9af/P590-534.pdf.aspx

In virtually all cases, and without regard to coating chemistry, the OEMs tell us NOT to remove their e-coat, and we do our best to comply while completely scuffing the part. It's the knock-off or reproduction parts mainly from overseas that everyone has to watch out for, or really, really old NOS (new old stock) parts.
 
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