Interesting video on Filler over Epoxy vs Bare Metal, Opinions?

B

BigKevO

New Member
I just came across a video where a guy tested the adhesion of filler applied to epoxy vs bare metal. I was planning on applying filler over epoxy as most people recommend on this forum but this video has me weighing the pro & cons of each process. In the video the bond between bare metal and the filler is stronger but it's not that simple. He tests the bond by sandwiching three washers together, on one side of the middle washer the filler is applied on bare metal, the other side is between two coats of epoxy. When he pulls them apart the epoxy side separates first. But wait teh interesting thing is the filler didn't release from the epoxy, the epoxy split leaving epoxy stuck to the filled and the washer. The force required to separate the bare washers is significantly stronger than the epoxy side. Now I am really confused. Living in southern CA I am not to worried about the filler absorbing moisture before I seal it with epoxy.

I know there are some variables like how long was the epoxy cured, how was the surface preped. But the weird thing is the epoxy must have bonded pretty well with both the filler and the metal because it does not pull of either surface, It actually splits.

Any thoughts?

Here is the video:
 
Here's the real test that needs to be performed:

Apply filler onto a bare metal test panel, prime and paint normally.

Apply epoxy then filler onto a bare metal test panel, prime and paint normally.

THEN, scratch or chip each one down to the filler layer, perform a 500 hour salt spray test, and see which one wins.

Filler on epoxy is about long-term corrosion resistance more than it is about adhesion. Both methods provide more than enough adhesion.
 
I have stripped enough vehicles to see that the cars where filler is applied directly to metal, more often than not, surface rust is starting to creep- also I noticed watching “bitching rides”, the shows from the first season or two I always wondered about why they did fillers on metal - but the newer shows always talk about sealing bare metal in epoxy first- they improved their process
 
Last edited:
Dave C 5 said:
I have stripped enough vehicles to see that the cars where filler is applied directly to metal, more often than not, surface rust is starting to creep- also I noticed watching “bitching rides”, the shows from the first season or two I always wondered about why they did fillers on metal - but the newer shows always talk about sealing bare metal in epoxy first- they improved their process
Click to expand...
I saw a recent episode where they restarted a project that sat in primer for several years. They found rust under the filler applied to bare metal. Was surprised how bad it looked.

Don
 
Stop watching YouTube videos and start reading threads here on the Forum:rolleyes:
First that test is not a proper comparison to applying filler over metal or epoxy on the panel of a vehicle. Second what type of epoxy primer? Not all epoxy primers are the same. If applying filler over bare metal was better do you think every OEM Manufacturer would require filler applied over epoxy to maintain the corrosion warranty?
If you want to watch a video go to YouTube and search "epoxy torture test".
When you apply filler over bare metal, what happens is the metal condensates because of the heat from the catalytic reaction that occurs when filler hardens. Then if it sits for any length of time bare or even with urethane primer over, it absorbs moisture from the air(humidity). Even in Socal.
 
Surface with epoxy was sanded with 220#, surface with bondo with 36#. Regardless of what brand epoxy was used, how long did it sit before applying bondo? Epoxy needs time for adhesion, and I would guess it did not have even 24 hours. As usual, another YouTube video done by an idiot, that only proves he knows nothing about conducting an experiment.
 
This is why if you dont know what you are doing, you dont post-tests on utube

*Who told him to use 220 on bare metal.

*Some epoxies dont do well with fillers
This is why FE with the question says call epoxy company.

*how long did the epoxy set per company before applying the filler?

*How long did the epoxy company tell him to let set before tearing it apart?
Some cured out in days, some months.

Oh, just pray he's not doing restorations for people.
 
Last edited:
If you watch it on youtube and read the comments, it will be clear that he is clueless about epoxy. The epoxy only dried over night before the test. He also said he thought epoxy stuck to the metal good, and it stuck to the filler good, it just separated. Seems more like a clueless attack on epoxy itself.
Here are a couple of his comments

Lakeside Autobody

​

Lakeside Autobody
4 days ago (edited)
If you watch closely, the epoxy primer stuck just fine to the metal AND it stuck just fine to the filler - it's weakness was that it split apart which to me says because of this, the filler could come away from the panel more easily. I plan on doing it again with different types of epoxy primer, letting , it cure for a week, a few days, 24 hours, etc. Thanks for the comment Icar - good to hear from you my friend

Lakeside Autobody

​

Lakeside Autobody
7 days ago (edited)
The epoxy dried over night. The epoxy was just not as tough as the plastic filler. One quick note... All shops that I've worked at frowned upon putting filler over anything but bare metal. It never felt good having other guys seeing you do it either. Have a good weekend Marcel :)
 
Last edited:
BigKevO said:
...Living in southern CA I am not to worried about the filler absorbing moisture before I seal it with epoxy.
Click to expand...
This is something I have not considered. I am in north Florida. My plan is to epoxy bare metal, wait for the appropriate amount of time, and apply filler where needed. What is the safe window for exposed filler before sealing with epoxy?

-----
Emil
 
I've said 1000's times my epoxy is flexible
To four inches thick, how much more can I go?
It took around 11 months to test the 4 inches thick with a sledgehammer, and since no one sprays it 4 inches thick, that is all I need to know.

You must know the product you are testing or wasting your time.
 
I knew where this thread was going just by reading the title. There are many of us on here that have learn to paint exclusively through this forum. It took a while for me to realize that looking at YouTube and the other auto body sites is counterproductive at best.
 
“ saw a recent episode where they restarted a project that sat in primer for several years. They found rust under the filler applied to bare metal. Was surprised how bad it looked”- dhutto01

Saw that- did you notice how thick the filler was !? Even my wife said “look how thick it is !” Surprised me . In their defense it had been sitting for a long time - I’m sure their process has become more refined over the years
 
Dave C 5 said:
“ saw a recent episode where they restarted a project that sat in primer for several years. They found rust under the filler applied to bare metal. Was surprised how bad it looked”- dhutto01

Saw that- did you notice how thick the filler was !? Even my wife said “look how thick it is !” Surprised me . In their defense it had been sitting for a long time - I’m sure their process has become more refined over the years
Click to expand...
Ya it was shocking. Have to wonder what was going on back then. I’m a backyard hack but I’ve never applied filler that thick. :D

Don
 
You must log in or register to reply here.
Back
Top