| Author |
Message |
Yannvanh
Samba Member
Joined: November 07, 2020
Posts: 144
Location: Belgium
|
 Posted: Wed Apr 17, 2024 12:15 am Post subject: Epoxy primer detaches from metal |
 |
|
I think i have a serious problem..
I blasted/sanded the whole underside of my 66 vw bus.
I then completely covered it with rust convertor for the last remaining corrosion. This product called Brunox en basicly is rust convertor and primer all in one..
Once it was all covered i sprayed 2 coats of epoxy primer then 2 coats of undersealer (novol for classic cars)
Now here's the thing..
I changed my mind on my rear setup and switched it to IRS. But with the heat from welding/grinding my undercoat and epoxy primer detached from the metal around that area.. heated it up in another spot with a torch (gently) and it does the same thing.. it started to bubble and you just can peel of the primer and undercoat
I don't think this is the normal way..
What should i do best? Take everything back off to bare metal and reprime it with maybe a raptor liner? (Always been a fan of that product but decided to go for a shine underside finish)
Thank!
_________________
'66 vw splitbus project:
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
Instagram page:
yannicks_splitbus_project
Always there to help! |
|
| Back to top |
|
 |
esde
Samba Member
Joined: October 20, 2007
Posts: 5993
Location: central rust belt
|
| Posted: Wed Apr 17, 2024 5:39 am Post subject: Re: Epoxy primer detaches from metal |
|
|
I would guess the epoxy isn't compatible with the rust converter, or something in the application was not right. Every epoxy I have used over blasted steel hangs on like a tick.
Here in the states, when I use OSPHO, we sand the steel again, after applying the ospho, as I have been told that the epoxy has the strongest bond directly over bare steel.
_________________
modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that. |
|
| Back to top |
|
|
Busstom
Samba Member
Joined: November 23, 2014
Posts: 3906
Location: San Jose, CA
|
| Posted: Wed Apr 17, 2024 9:50 pm Post subject: Re: Epoxy primer detaches from metal |
|
|
| Quote: |
I blasted/sanded the whole underside of my 66 vw bus.
I then completely covered it with rust convertor for the last remaining corrosion. This product called Brunox en basicly is rust convertor and primer all in one. |
I believe you mistakenly used the Brunox; the Brunox is intended to be applied directly over RUST, not onto a "blasted/sanded" finish. That is presumably how the Brunox achieves its bond to the substrate, as the Brunox instructions specifically state to brush off loose rust and other contaminants and then apply Brunox over the remaining porous rust surface. If you blasted/sanded your undercarriage, you should've gone directly to epoxy primer.
POR-15 here in the States is similar, in that it's intended to go onto/into porous rust, not stripped surfaces, else the bond is compromised. There have been many complaints here about POR-15 for failures in this scenario.
And as already mentioned, you may be having material compatibility issues as well, but if it's peeling down to metal, I suspect the Brunox did not bond properly. A quick read on how rust converters work indicates that they depend on present rust to convert into the desired base/foundation that they are designed to create...I suspect your remaining corrosion was not enough to perform as intended.
_________________
My name's Steve and it's pronounced "Bust 'em" (cuz people think I'm Tom) 😏 |
|
| Back to top |
|
|
Bulli Klinik
Samba Member
Joined: January 16, 2005
Posts: 2090
Location: Bulli Klinik, Colorado Springs
|
| Posted: Thu Apr 18, 2024 6:31 am Post subject: Re: Epoxy primer detaches from metal |
|
|
The phosphoric acid needs to be neutralized prior to epoxy.
The same thing happened to me, once.
_________________
I've never met a Bus I didn't like.
Mike K
Bulli Klinik
Colorado Springs |
|
| Back to top |
|
|
Evil_Fiz
Samba Member
Joined: May 06, 2011
Posts: 1056
Location: Jacksonville, FL
|
| Posted: Fri Apr 19, 2024 5:21 pm Post subject: Re: Epoxy primer detaches from metal |
|
|
| Bulli Klinik wrote: |
The phosphoric acid needs to be neutralized prior to epoxy.
The same thing happened to me, once. |
Epoxy does not play well with acid treatments. I covered my entire car with phosphoric acid before I learned this fact. I did an adhesion test and found that epoxy WILL adhere to metal that is sanded with 80# AFTER it is treated with acid. Here is a link to the post covering the subject: https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=
At this point, your best course of action is to take the surface back to bare metal by blasting or sanding with 80#, clean it well with wax and grease remover, then apply 2-3 coats of epoxy. I imagine this is not what you want to hear but take it from someone who had to sand a car to bare metal twice, it IS worth the effort.
-----
Emil
_________________
“…It's not just about what's interesting. It's also about what's helpful, and it's helpful even if it helps just one other guy working on a Ghia.”
kiwighia68
See my build on TheSamba at:
The K_R_A_K_E_N_N : a 70 Ghia Convertible reinterpreted |
|
| Back to top |
|
|
74 Thing
Samba Member
Joined: September 02, 2004
Posts: 7410
|
| Posted: Fri Apr 19, 2024 5:33 pm Post subject: Re: Epoxy primer detaches from metal |
|
|
You have either mechanical (sanding) or chemical adhesion.
You tried chemical and it did not work so go with the sanding as suggested above. |
|
| Back to top |
|
|
Onceler
Samba Member
Joined: May 28, 2010
Posts: 1647
Location: Indiana
|
| Posted: Fri Apr 19, 2024 5:57 pm Post subject: Re: Epoxy primer detaches from metal |
|
|
I guess I don’t understand the problem. Epoxy always detaches due to intense heat from welding or a torch.
I just sand it back until it stops and re-apply.
_________________
1972 Karmann Ghia |
|
| Back to top |
|
|
Evil_Fiz
Samba Member
Joined: May 06, 2011
Posts: 1056
Location: Jacksonville, FL
|
| Posted: Sat Apr 20, 2024 6:16 am Post subject: Re: Epoxy primer detaches from metal |
|
|
| Onceler wrote: |
I guess I don’t understand the problem. Epoxy always detaches due to intense heat from welding or a torch.
I just sand it back until it stops and re-apply. |
The heat is accelerating the delamination of the epoxy; it WILL eventually fail. If properly bonded to the substrate, it would bubble and crack, but not detach. Epoxy, for lack of a better analogy, is tinted glue.
- Sand or blast all the epoxied areas back to bare metal.
- Make sure you have sanding/blasting scratches on the entire surface. Because you used acid, blasting is the better choice. Make sure none of the old products remain on the metal.
- Get both solvent-based and water-based wax & grease removers (W&GR).
- Wet the surface with the solvent W&GR then wipe it dry with a clean, lint-free towel. Repeat this step until the towel comes up clean. A ZEP spray bottle works well for wetting the surface.
- Then, wet the surface with the waterborne W&GR and wipe it dry with a clean, lint-free towel. Repeat this step until the towel comes up clean. You will need an acetone-resistant spray bottle for this one. Otherwise. soak a lint-free towel in W&GR to apply.
- Disposable Blue shop towels are a good choice. They will lint a bit but you will most likely sand the epoxy or apply filler over it.
- Finally, spray the epoxy onto the bare metal.
- The solvent-based W&GR will remove grease and other heavy contaminants.
- The waterborne W&GR will remove organic materials such as skin oils.
Please ask for clarification if you are unsure of what I described. PM me for product recommendations on the W&GR.
-----
Emil
_________________
“…It's not just about what's interesting. It's also about what's helpful, and it's helpful even if it helps just one other guy working on a Ghia.”
kiwighia68
See my build on TheSamba at:
The K_R_A_K_E_N_N : a 70 Ghia Convertible reinterpreted |
|
| Back to top |
|
|
Kb65single
Samba Member
Joined: July 24, 2019
Posts: 276
Location: Obxnc
|
| Posted: Sat Apr 20, 2024 4:22 pm Post subject: Re: Epoxy primer detaches from metal |
|
|
| Onceler wrote: |
I guess I don’t understand the problem. Epoxy always detaches due to intense heat from welding or a torch.
I just sand it back until it stops and re-apply. |
I too don’t understand the problem. If you weld on the back side of ANYTHING it will bubble smoke burn and end up being a charred mess and separate from the metal. Like Oncerel says, sand it back and reapply.
Ken |
|
| Back to top |
|
|
MuzzcoVW
Samba Member
Joined: February 21, 2018
Posts: 1503
Location: Westfield, MA.
|
| Posted: Mon Apr 22, 2024 10:36 am Post subject: Re: Epoxy primer detaches from metal |
|
|
| Kb65single wrote: |
| Onceler wrote: |
I guess I don’t understand the problem. Epoxy always detaches due to intense heat from welding or a torch.
I just sand it back until it stops and re-apply. |
I too don’t understand the problem. If you weld on the back side of ANYTHING it will bubble smoke burn and end up being a charred mess and separate from the metal. Like Oncerel says, sand it back and reapply.
Ken |
This, as stated above! Also, after blasting the rust should be gone, so no converter should be used. Epoxy primer goes directly on the freshly blasted metal... after rust has been mitigated. A rust "converter" will do nothing to keep rust from forming, epoxy primer can if used correctly |
|
| Back to top |
|
|
Yannvanh
Samba Member
Joined: November 07, 2020
Posts: 144
Location: Belgium
|
| Posted: Thu May 02, 2024 4:48 am Post subject: Re: Epoxy primer detaches from metal |
|
|
Thanks for the comments guys,
I am taking everything back to bare metal:
Here's a picture of the undercoating dat detaches:
Its a big job but i am happy that i discovered it now prior to the bus being completely finished..
After bare steel i gonna sandblast everything again so its clean, degrease it and shoot 2-3 coats of epoxy..
_________________
'66 vw splitbus project:
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
Instagram page:
yannicks_splitbus_project
Always there to help! |
|
| Back to top |
|
|
MuzzcoVW
Samba Member
Joined: February 21, 2018
Posts: 1503
Location: Westfield, MA.
|
| Posted: Thu May 02, 2024 4:56 am Post subject: Re: Epoxy primer detaches from metal |
|
|
| Also to go along with what I said above... Make absolutely sure to read the specific requirements for the primer you choose to use. SOme require a metal etch primer before epoxy, and some are DTM. It's always follow the manufacturers instructions. Also make sure you aren't painting in too low a temp. Even overnight temps need to be taken into consideration when painting, especially catalyzed products |
|
| Back to top |
|
|
|
