Is this rust or air bubbles in the bondo?

[darth_linux]

So I’ve got this showing up in a few places where this is a skim coat of bondo. Is it rust coming through or air bubbles from the bondo that got trapped by the paint? Paint job is somewhere between 6 and 15 years old, I’m guessing.

 

[cbarge]

That is moisture coming up through the poor prepping of the panel.
Eventually the bondo will delaminate and expose rusted metal.
Cowl covers are thin to begin with and very common for them to blow out.

I had 3 cowl covers I stripped and NFG once they reared their fugly peppered pinholes.

Get a good southern one, sandblast it and cover it in epoxy primer.

 

[darth_linux]

That is moisture coming up through the poor prepping of the panel.
Eventually the bondo will delaminate and expose rusted metal.
Cowl covers are thin to begin with and very common for them to blow out.

I had 3 cowl covers I stripped and NFG once they reared their fugly peppered pinholes.

Get a good southern one, sandblast it and cover it in epoxy primer.

About how many years do you would think it would take for moisture to start doing this? Trying to guestimate how old this paint is.

 

[cbarge]

About how many years do you would think it would take for moisture to start doing this? Trying to guestimate how old this paint is.

Improper or poor prepping will show its ugly head within the first couple years after bring exposed to the outside elements.
But that does not help determining the age of the paint job.

 

[cbarge]

The Boab' s paint is 8 years old.
After losing storage while building our garage, bubbling started after 1 summer being exposed to the elements parked outside..
Ya' ll know I prepped the **** out of this car with lots of rust convertor, DOM16 and epoxy primer..yet rust never sleeps.

 

[darth_linux]

The Boab' s paint is 8 years old.
After losing storage while building our garage, bubbling started after 1 summer being exposed to the elements parked outside..
Ya' ll know I prepped the **** out of this car with lots of rust convertor, DOM16 and epoxy primer..yet rust never sleeps.

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Wow! That’s crazy. My bubbles are like little pinholes. Have you seen those before, or just the larger bubbles like on Boab?

 

[MONC440]

Rust grows so it starts as small and will continue to grow until you remove it. Left untreated those pin hole bubbles will become larger. This could take years or months depending on how the metal was prepped.

 

[cbarge]

Wow! That’s crazy. My bubbles are like little pinholes. Have you seen those before, or just the larger bubbles like on Boab?

I aeen yours before on the cowl covers

 

[Ross Wooldridge]

The Boab' s paint is 8 years old.
After losing storage while building our garage, bubbling started after 1 summer being exposed to the elements parked outside..
Ya' ll know I prepped the **** out of this car with lots of rust convertor, DOM16 and epoxy primer..yet rust never sleeps.

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What a shame, Leaburn. That must break your heart to see that.

 

[cbarge]

What a shame, Leaburn. That must break your heart to see that.

Shame yes but no broken hearts.
It get driven and sometimes caught in the rain when not at home.
Oh well nothing you can do honestly.
The way these cars were designed, water will find places to well up.

 

[66/440]

If you choose to strip either this one or another be careful when sand blasting. Sand blasting can drive rust deeper into the work piece sometimes it is so small as to be undetectable with the naked eye. That's part of the reason many restorers use alternative methods ( plastic media or chemical). When rust is left in a panel no matter how small it will "grow back" eventually. Ospho (phosphoric acid)or other chemical treatments work well on stopping this after panel has been stripped. Best results are obtained if the part can be submerged. If that is not an option old towels duct taped to a panel and wetted with your chemical of choice to maintain contact with the panel works well. Keeping the liquid in contact with the panel and not allowed to dry produces best results. As always personal protection equipment is recommended. If you are searching for a new panel as an alternative to Murray Park if he doesn't have one you can try Clay and Sons, southwest of St. Louis MO.