Question about Rust Bubbles on Car

[jhorton6]

I have a 2006 Pontiac Vibe. The last couple years I have been noticing more rust bubbles appearing on the roof of the car. From what I can see from looking at other Vibes this looks to be a common issue as I have seen the same thing on other Vibes.
A couple have chipped off and I have touched up with touch up paint. Others are still just showing as bubbles.
The one thing I don't understand is when I leave them for 2 or 3 weeks and as the car is parked outside when I go and look at them again they have a white oxidization around some of the edges of the bubbling. If I take my wet finger and really rub at them I can get the oxidization to disappear. But again a few weeks later (sometimes just days) the oxidization is reappearing. There doesn't appear to be any crack or break in the paint.

Can anyone explain what might be going on? I know they are rust spots, but is there any way to slow down whatever is going on with the oxidization or whatever it is that is occurring? There are a couple similar spots that I have never touched and have not done this.

I wasn't able to get a picture, but hopefully someone can help me with this.

Thanks

 

[Accumulator]

Hope it's not rusting out from the inside, that'd be a "try to get GM to fix it" issue.

Assuming it's not that, then the fix that I use is:

-Clean with PrepSol-type solvent
-Grind out each bubble/chip with a diamond bur on a dremel
-Treat bare metal with something like MetalBlast or Metal Ready
-Prime (I use a paint-over-rust" product, my faves being Rust Bullet or KBS Rust Seal)
-Apply touchup paint

The paint/clear is compromised by whatever started the issue (probably a chip or un-maintained micro fissure/porosity issue in the paint) so you're gonna get stuff like that oxidation. This is an unfortunate example of why it's critical to detail areas like the roof of tall vehicles (areas you normally can't see) just like the rest of the vehicle. If the roof paint was especially porous, keeping it all sealed up with an LSP could be more critical than usual.