I had some bubbles like this on the bottom of my GP doors.

It never got any worse. Not sure if it is the sameting but it looked similar.

I thought it was rust and it never got worse. I messed with it and it was not rust. Not sure what it is but it was not rust.

 

Had this on mine since I bought it used. Shouldn't really be doing it, since the HHR has only been in 2 winters, and from the looks of it it looks like it was taken care of before I got it...

 

I just had mine in to be redone, originally "fixed" in october. After the winter the rust was more prominent along the whole bottom of the front doors. The district service manager had to be involved with the repeat repair.
I told them this would happen, but apparently all they can do is strip the paint and repaint it. I asked about some kind of anti-rust gelcoat like they use to restore old cars, but they said "primer is primer".
Their opinion is that water gets in the door, seeps around and back up the seam. I think its possible the top of the seam is attracting dirt and moisture as it felt porous when new. Not sure what the cause is, but apparently it has to be fixed every few months with a repaint.
If I had it to do over again, I would have just touched up the bubbles myself. As it is I will spray in some rust check and hope for the best I guess.

 

I have the SS with the smooth ground effects version of a running board, which in essence, has the same protective qualities that the running boards provide.

I have no rust or bubbling on the bottom edge of my doors. My HHR is just over 2 yrs old; just over 15k mi.

 

What my dad and I did was clean the water drain holes really good, then we sprayed a can of rustproofing into the doors. We sprayed enough until it would run out of the holes. Did it to all doors, the hood, and the liftgate. Oil would work too, but after a while it would need to be re-done. This rustproofing hardens and is there for life.

 

I also wash and dry the jambs when I wash the car.

 

I usually do this in the winter, more than summer, but I ALWAYS dry them out completely. If I have the time I will also leave the doors open so they can air dry as well. I believe water has quite a bit to do with the rusting...

 

good luck , my 07 is still under warranty ive had the bubbles removed and painted under warranty in december and its back again......

 

Yeah, it seems like everyone who has had them "fixed" has had them come back, and most of the time they're worse. I think I'm just going to leave mine be... A car this new really shouldn't have this issue...

 

No problems here on an '07 with running boards. I wonder if chipping starts the issue?