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paint keeps cracking ?


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#1 _Shelly`s LX_

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Posted 11 April 2014 - 07:15 AM

car was bare metal bogged up where needed and rust conversion where needed [i did go overboard with the rust conversion goop] =prep wash ,etch primmer,primmer surfacer,sparay putty ,guide coat sanded well  weeks later noticed cracks in hatch channels and around door jams .so we sanded thinking it was rust conversion so we took all channels and door jams back to bare metal noticed in channels under cracked sections was bogg ,then we sanded out rust conversion stuff, then i prep washed etched primmer spray puttied and guide coat left for weeks ,cracked again ? !wtf! sanded all out again bare meatal preped and etched and left for weeks and cracked again even where the tail lights sit in there [terrible place to sand ] flat panels all good but its in the corners 90 degree angles thought spray putty shrinking pulling it all of =wasnt used last time it still did it

cold weather coming i cant get passed spray putty  we saying = its the etch ,its the spray putty,its the bogg ? please help which one is it  IMG_3886.jpg



#2 Rockoz

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Posted 11 April 2014 - 08:37 AM

If thats a join between panels I would be using seam sealer not bog.

The seam sealer will be flexible enough not to crack.

Either that or fully weld.



#3 TerrA LX

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Posted 11 April 2014 - 08:49 AM

Rockoz be spot on there.

Edited by TerrA LX, 11 April 2014 - 08:50 AM.


#4 sibhs

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Posted 11 April 2014 - 09:28 AM

If thats a join between panels I would be using seam sealer not bog.

The seam sealer will be flexible enough not to crack.

Either that or fully weld.

Surely not that simple. I can't imagine Shelly redoing the same repair many times over and not realising it's a seam crack. 

 

Too thick, drying too fast, I've actually got no idea.  :-(

 

Marty



#5 minor miss steak

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Posted 11 April 2014 - 10:30 AM

Had a problem like that but it took a couple of months before it showed up ( it was on a door of my LJ) so it was painted over by the time I noticed it (total bummer), welding it was the only way to solve it, so I'm with Rockoz.



#6 slar

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Posted 11 April 2014 - 01:21 PM

Bare metal again.....2k epoxy (Epotec 408)....fill (use good quality....evercoat gold )... epoxy.....high fill prime ....block flat ready to paint.
Use epoxy....no need for etch....excellent corosion protecton and filler adheres well to it.

Sounds like too much film build up to quick to me....this will cause heaps of shrinkage and cause your problem.

#7 slar

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Posted 11 April 2014 - 01:24 PM

Oh yeh if it is a seam....after the first coat of epoxy use seam sealer

#8 TerrA LX

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Posted 11 April 2014 - 01:26 PM

Sikaflex.

#9 _Shelly`s LX_

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Posted 13 April 2014 - 08:30 PM

NO APPARENTLY ITS ME = THE WAY I PREP THE CAR ? GRRR



#10 _Bomber Watson_

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Posted 13 April 2014 - 08:42 PM

Im gonna roll with the general consensus of to much to fast. 

 

Slar is pretty well on the money. And Terry ment to say Sikaflex 221....

 

Cheers. 



#11 mitchg

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Posted 14 April 2014 - 01:45 AM

Just curious for my own learning. Could the way the bog is mixed cause this? Or the bog being off?

#12 TerrA LX

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Posted 14 April 2014 - 05:38 AM

I've seen too much hardener in body filler bleach thru the colour in the top coat.

With anything I suppose, use it within a year or 3 of buying it and always follow manufactures recommendations.

And yes sikaflex 221 rules supreme.

Edited by TerrA LX, 14 April 2014 - 05:39 AM.


#13 _Shelly`s LX_

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Posted 16 April 2014 - 04:46 PM

i thought it was old bog = but there have been cracks where no bog is  :banghead:



#14 Rockoz

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Posted 16 April 2014 - 05:41 PM

Incompatible coatings?

What are you putting on top of what?

Is this over bare metal or something else?






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