Technical Another Paint Failure 35 Buick

Nice job. Those big Buicks have always been one of my favorites. Should be a great highway cruiser.

Gary

 

Nice!

 

That Came out great !!

This is a subject that's close to home for me.
I'd really like to hear the chemistry, maybe point me to where to find it?
I'd also like to know what procedure in blocking and guide coating is skipped and missed that allows metal or filler to pop thru on a final primer sanding that's wet?

Maybe it's wrong, maybe it's extra steps, but here's the order how I do it, perhaps this is why I'm having trouble understanding how a breakthrough happens on final wet sanding causing the issue.
metalwork, filler work, guide coat, really tight filler/ icing work if needed, guide coat again for highs and lows if the guide coat is all over the place it's more than obvious that there needs more bodywork right?, maybe a few coats of spray polyester , if and when no highs and lows show then epoxy prime, everything is sealed and locked down, high build primer, block sand and stop sanding if the epoxy shows which very rarely because it was already guide coated. Now bring in the water if you think it's needed.

I've seen guys throw cases of high build thru the gun and sweep it off the floor. I hate icing on top of the high build, it happens but it is avoidable. I've seen guys taping down high spots after "their final" sand and then have to blend in primer and final sand. I'm kinda fussy and to me this here stuff is where the extra steps and time is waisted.

 

Paint guru, Did you see that ^^^
Just wondering if you had a comment or going to leave it alone

 

This is very interesting, i thought etch was the way to go. So does epoxy have an etching component in it?

 

Sorry my app never updated that anyone else responded. I posted these same pictures of this on my wife's new paint delivery van


That was once bare shiney metal and filler on top. You can actually see a rust line developing in the filler, this had a very thin coat of something over the top but moisture eventually got through. This is the start of a bodyfiller crack...

Once moisture gets under body filler that is directly on metal, the rust will start to form underneath. The reason is bodyfiller is porous, so oxygen and moisture can both be present.
Now not all epoxy primers are created equal either. If the epoxy doesn't have moisture scavengers the tiniest bit of moisture in your airlines can create rust pockets that create these tiny bubbles 6 months to even 5 years down the road. What the moisture scavenger does is basically push all the moisture off the surface and the moisture helps aid in the curing process, it uses moisture on the surface and then uses moisture in the atmosphere to help cure completely. We developed the dtm reducer using the same moisture scavenger in a solvent blend for people to spray in dips, valleys or in cracks that paint would be too thick to get into, but that dtm reducer is in our epoxy, it's also a rust encapsulator so if there were flash rust there that you didn't see it would encapsulate it. No bodyfiller can do all this, that's why it's important to use epoxy as your foundation.
As far as etch primer.... Not a fan... It's technically a 1k primer that can dry but can be reversed back into a liquid. I am no fan of sandwiching 1k products between 2k products. Also you can not put bodyfiller directly onto self etch the heat in the bodyfiller curing process effects adhesion and ***anium dioxide which is in a lot of bodyfiller is not compatible with acids.
As far as sanding through on blocking, here is a good process... After epoxy priming block sand the entire vehicle with 180. This will reveal all the high spots around every dent.... This is the main cause of sand through spots, everyone fills the dent but there is a high spot all around the dented area. This is where a slap s**** and dolley comes in handy.

Once all your rough in work is done on top of the epoxy any bare metal spot larger than the size of a basketball needs another coat of epoxy. Then comes high build urethane primer and blocking, or use polyester primer. I personally think urethane sands better. But for that super slick paint job it's going to take multiple prime and blocking attempts. But that's the difference in trailer queens and regular paint jobs.

Sent from my SM-N920V using The H.A.M.B. mobile app

 

Thanks paint guru- but that still leaves the same original questions in my earlier post,,
pertaining to your example of being at the final coats of primer, water sanding and sanding thru to filler or bare metal.


For decades and decades filler went on fresh clean toothed up bare metal. Somewhere it changed to epoxy on bare metal and then filler on epoxy. When did that thinking change?

So looking at your latest example above, that brings up new brand questions,,, that bodywork on the panel truck was not ever finished and never protected under much. So the fillers and primers were destin to fail from moisture, correct? And how would an epoxy underlayment base prevented that failure?

 

The epoxy is not porous, so it creates a moisture resistant barrier.
The epoxy then body filler concept came in the early 90's when Akzo Nobel really started showing benefits of 2k epoxies in automotive. This also came about when extreme weather chambers became available to do testing. Before the only way you could test durability is just by waiting. In a extreme weather chamber every 24 hours is equal to about a year in the real world. So what before took 10 years to know what would happen, we can now know in about 10 days. Basically we repair or coat a panel, let it go through a full cure (7-30 days) then it goes into the chamber.
One way to look at this is bottom line we all know moisture is bad for bare metal, so 2 things metal needs to stay complete is moisture resistant with corrosion protection - there is only one product that adheres very well to metal that can provide both of these functions and still be flexible and that's epoxy even at very high mil build.
So as long as epoxy goes on first then filler then your high build, as long as you don't break through to your epoxy wet sanding, it will stay protected from moisture. If you sand through to your bodyfiller wet sanding, I would highly advise you to let it dry out a couple of days before priming over the top so that you don't have moisture trapment. This can / will cause paint delam. Hope this helps answer your question, my mind is thinking a lot quicker than I can type.

Sent from my SM-N920V using The H.A.M.B. mobile app