Filler to bare metal causing metal to sweat ! What

F

fastwayfirebird400

I've never heard of this so I'm asking the board here.

I was talking to an old timer (65) and we got around to talking about filler to metal or filler to epoxy. He stated that he didn't like applying the filler to bare metal because if you mixed up the filler too hot it could cause the metal to sweat causing moisture and possible rust to form down the road.
I bet he had filler back in the day that absorbed moisture from wet sanding or poor prep that may have been the culprit.

I find it interesting how beliefs are passed down to others that are just learning and often times just accepted without even asking why and applying some logic to it.
 
There's nothing wrong with filler over bare metal.
It'll outlast us all when done properly.
I will tell you this, and it will upset a few, but a friend of mine
had filler over epoxy and bare metal on the same qtr panel
that he applied properly and when the panel was hit, only
the filler over the epoxy came off.
No one wants to hear that.
I'll stick with filler over bare metal, it's a time tested procedure.
(there, I said it):p
 
jcclark;16095 said:
There's nothing wrong with filler over bare metal.
It'll outlast us all when done properly.
I will tell you this, and it will upset a few, but a friend of mine
had filler over epoxy and bare metal on the same qtr panel
that he applied properly and when the panel was hit, only
the filler over the epoxy came off.
No one wants to hear that.
I'll stick with filler over bare metal, it's a time tested procedure.
(there, I said it):p
Click to expand...

me too.
 
I noticed a test in an old thread that resurfaced on Hodrodders http://www.autobodystore.com/filler_&_epoxy.shtml
And it made a lot of sense to me, but the more I thought about it, the more it didn't seem right that the epoxy would break into. So I did my own test with the same epoxy he used and determined that the test was flawed like someone on Hotrodders said.

Its flawed because the epoxy didn't have enough time before the filler was applied, and didn't have enough time to cure before the test. Filler would break long before the flexable epoxy, a thin coat can bend 90 degrees. Barry may shoot me down, but it seems to me that the 7 day recoat window is playing it safe for ppg, so at that point its certainly not cured but the filler is completely cured.

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Last edited by a moderator:
fastwayfirebird400;16091 said:
I've never heard of this so I'm asking the board here.

I was talking to an old timer (65) and we got around to talking about filler to metal or filler to epoxy. He stated that he didn't like applying the filler to bare metal because if you mixed up the filler too hot it could cause the metal to sweat causing moisture and possible rust to form down the road.
I bet he had filler back in the day that absorbed moisture from wet sanding or poor prep that may have been the culprit.

I find it interesting how beliefs are passed down to others that are just learning and often times just accepted without even asking why and applying some logic to it.
Click to expand...

I disagree with his reasoning, although I would never use filler over bare metal, I tell people all the time on the phone everyday, its your choice and its been working for 60 years that way.
 
jcclark;16095 said:
There's nothing wrong with filler over bare metal.
It'll outlast us all when done properly.
I will tell you this, and it will upset a few, but a friend of mine
had filler over epoxy and bare metal on the same qtr panel
that he applied properly and when the panel was hit, only
the filler over the epoxy came off.
No one wants to hear that.
I'll stick with filler over bare metal, it's a time tested procedure.
(there, I said it):p
Click to expand...

Filler coming off epoxy first, i call bull, unless it was a test set up for failure, most likely INTERNET BS.
 
Chevman,
Good test and the SPI is even more flexible, that is why it dries slower.

I have 3-5 pucks 3-4 inches thick, dried out in a quart painters pail and after about six months you can barley bend it, just to know there is a little flex but you could never break it, with out cutting.

Had a few only an 1/2 inch thick and ends can be bent to touch ends. Cannot break.
 
So the post I guess has really splits into two question the first one has been beat to death will the 36 to 80 grit scratch provide more of a mechanical tooth for the filler to latch to or the chemical reaction holding ability of filler to epoxy. There is true believers on both side and both ways appear to have been working.

The 2nd question, can moisture form behind filler to metal because to filler was mixed with activator hot enough to cause moisture?


I personally apply filler over bear metal myself but it seems that if you allow the epoxy to cure out for a good length of time then that's good too. There are pros (I don't fall into that camp) that are on both sides of the fence that have outstanding work that still shows years down road.
 
fastwayfirebird400;16107 said:
So the post I guess has really splits into two question the first one has been beat to death will the 36 to 80 grit scratch provide more of a mechanical tooth for the filler to latch to or the chemical reaction holding ability of filler to epoxy. There is true believers on both side and both ways appear to have been working.
-------------------------------------------------------------------
If the epoxy is less then seven days old, sanding does nothing for adhesion.
After 7 days anything courser then a 180 BY HAND (not DA) 80 if DA is all you need.
This is SPI epoxy only and not sure how the others work.
----------------------------------------------------------------

The 2nd question, can moisture form behind filler to metal because to filler was mixed with activator hot enough to cause moisture?
-----------------------------------------------------------------------------
I say sounds good but bull, if it did the filer would suck it up anyways and my big worry is filler maintaining solvent and air anyway, that is why I want the epoxy under it.
-----------------------------------------------------------------------------


I personally apply filler over bear metal myself but it seems that if you allow the epoxy to cure out for a good length of time then that's good too. There are pros (I don't fall into that camp) that are on both sides of the fence that have outstanding work that still shows years down road.
Click to expand...
Bottom line is this.
Of all the calls I get from pros doing everyday insurance work 99% are putting body-filler over bare metal.

Of all the calls I get from Restoration and custom shops, I will say 99.9% are using epoxy first, cannot remember the last time someone told me they were not.

EDIT
(sorry this is a mess but I don't have time to fix now, hopefully you all can figure out my answers. LOL)
 
I normally follow the manufacturers advice
Click to expand...
Which one ! Most Filler says to scratch with 36-80 grit on the metal, Paint mfg want filler on top of it! It's like there's a fight to get to the metal first as one manufacture doesn't want to chance their product being mistakenly blamed because of the failure the first product (understandably so).
 
jcclark;16095 said:
There's nothing wrong with filler over bare metal.
It'll outlast us all when done properly.
I will tell you this, and it will upset a few, but a friend of mine
had filler over epoxy and bare metal on the same qtr panel
that he applied properly and when the panel was hit, only
the filler over the epoxy came off.
No one wants to hear that.
I'll stick with filler over bare metal, it's a time tested procedure.
(there, I said it):p
Click to expand...

Filler over bare metal- It's a time tested proceedure that will fail in road salt country if the paint surface is ever compromised-rock chip...
 
Thank you Bob. I knew if I read long enough, you would get to the point about chips and moisture. People don't think about what happens when the paint surface is compromised. The filler will absorb the moisture, and if it is applied directly to the bare metal, the metal will be rusting out very shortly after that.

Now.... I have seen the reports of the so called "tests" where the filler came off the epoxy coated panels. I can tell you that I performed my own test several years ago when the talk of this first came out. I destroyed the meatl trying to get the filler off the epoxy. Of course, I didn't apply the filler the day after I applied the epoxy then the next day beat it on a table edge. I waited for a couple of weeks until the stuff had a chance to cure. Then again, in all reality, if I had applied filler on top of epoxy and the panel went thru that much damage, I would not be concerned if the filer came off or not. The panel would at minimum, need to be stripped to be repaired.

Now... I currently work in a collision shop. That means that I do apply the filler on bare metal AT WORK. At home, where I do restoration type work, I apply epoxy first. If there is a failure of any type on the work at home< have to repair it at my cost. I am going to make sure it is right the first time!

Aaron
 
I think what they are getting at is you want a protective wall between the filler and metal.
 
OJ.... That is exactly the point. Any vehicle that is driven on the road is subject to getting paint chips. If the paint is chipped, even if the filler is sealed with epoxy, it is likely to get wet because the epoxy is likely to get chipped also. The idea isn't as much to keep the filler from getting wet, but more to keep the metal from getting wet. The filler WILL absorb moisture, but if it is applied on top of epoxy, the moisture can't get to the metal.

Aaron
 
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