# worried about body filler failure



## woolsey10 (Oct 18, 2011)

unfortunately i do not have a garage or shed i can keep my car in while i do the body work. i have to keep it under a heavy duty tarp. and due to the poor weather i haven't been able to uncover it and work on it for a few weeks. i have the front end and roof sanded and bondo is shaped and sanded but it is not primered yet. there was some good weather yesterday so i took off my tarp only to find out that there are holes all over it and a lot of rain has gotten on the car. i found that one spot of bondo has a bunch of bumps, i'm guessing from moisture so i'll have to grind all that off and redo it? this is my first restoration and i'm just learning as i go. so far only one spot of bondo has failed. so does that mean the rest is fine or should i be worried about the rest of the bondo soaking up moisture and failing in the future? i don't want to get my car painted and then the bondo underneath crack or bubble or anything like that.


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## AMT1379 (May 11, 2010)

Not sure about the bondo, but can you put up one of those pole & tarp portable garages? There were selling at Harbor Freight for less than $200. May provide more protection, at least temporarily, than the tarp.


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## woolsey10 (Oct 18, 2011)

well i have a family member about 20 minutes away from where i live that has a shed i can use, but i need to get some welding done here in town before i take it there. i'm not worried about the protection right now i just need to know if i should re do all of the bondo that i've done or if it will be alright as it has not yet failed. any answers would be greatly appreciated.


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## ALKYGTO (Mar 29, 2010)

Sorry to say but Bondo absorbs moisture like a sponge and what you have done will have to be removed and reapplied. 

Better now than when you have a shiny topcoat on it though. Even some rattle can primer can be used to seal it up temporarily when doing the bodywork.


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## Instg8ter (Sep 28, 2010)

:agree it will come back to haunt you. Your best off prepping the ground bare metal with epoxy primer before applying any fillers also.


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## Geeza71 (Apr 22, 2013)

:agree X2
The moisture soaks into the bondo and forms a layer of surface rust on the steel underneath if left wet too long. This will cause it to peel away. Usually after the paint job is finished. Even if it doesn't peel it will most likely blister the paint as the moisture evaporates.
When you sand it off look out for surface rusting. If you see it at least you'll know it was worth the extra work to re do.


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## 05GTO (Oct 6, 2004)

Instg8ter said:


> :agree it will come back to haunt you. Your best off prepping the ground bare metal with epoxy primer before applying any fillers also.


:agree

It may be a good idea to treat the bare metal with *Ospho* prior to spraying with a good epoxy sealer/primer.

Under the tarp the car will hold humidity that will rust the car quicker than anything. Wait till you can use the shed before starting the stripping, treating and priming, do one section at a time.

JMHO


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## nineteen 65 (Jul 8, 2013)

I agree with all the replies that you received to your question. Body filler is typically composed of polyester resin, glass beads (light weight variety) and talc. Fillers should never be used when the substrate and uncoated body work could get subjected to moisture as this will lead to eventual failure. 
Rereading your post I am not clear on your comment ' i found that one spot of bondo has a bunch of bumps'. A properly cured application of body filler should not have bumps appearing after you worked the cured patch. You could get peeling and loss of adhesion due to your moisture issues. If you get post cure bubbles you may have another problem due to either bad mixing; resulting in unreacted styrene or use of filler and BPO initiator that has exceeded its shelf life, or bad cure of the patch due to working temperature. Work in a clean dry environment, warm ambient temperature, proper substrate preparation and the use of fresh filler and initiator. Only buy your supplies from a reputable body shop supply house that has good turnover of product. These products do get old and to the untrained eye will still look fit for use.


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## geeteeohguy (Feb 2, 2008)

Back to basics, here. Bare metal should not be left exposed for more than a few minutes, maybe an hour maximum if you want your paint job to last. Moisture in the air (not so much in Utah) will start flash rust that you can't see....until it bubbles the paint up 5-10 years later. Strip one small area at a time, treat it with metal prep, and prime it with epoxy based primer right away. And, one other thing: cars out in the elements don't do very well.


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