Plausible, Oldblue is an outdoor HHR, the door bubbles came up in 2011 and GM repaired in 2012.
body shop manager, said the problem was the seam sealer at the bottom of the door were the outer door skin folds over the inner door structure.
It still hasn’t resurfaced since that time. They redid the rear hatch bottom seam , also.

Now, Sweetie’s Sunfire was a garage kept car, at 16 years old , no door rust, no typical rust like Cavaliers and Sunfires , that rot on the left rear 1/4 panel near the fuel door. Our garage is not heated , just insulated.

 

Mine is garaged as well. And rarely driven in wet winter.. So doors are like new.

Wife's Mopar gets driven year round, but is garaged as well. Her doors are rust free also.

 

My "07 2LT has rust in the bottoms of three of the four doors. RF door is rust free. No reason why.....?

In any event, I sanded down all the rust bubbles with a rotary flap-type sander until I got to bright metal. Then, I coated the exterior with Eastwood "Rust Encapsulator" and sprayed Eastwood "Internal Frame Spray" into the bottoms of the doors with the included spray extension.. Then, after it all dried, I painted the door bottoms with a spray paint I had color matched at Finishmaster. Took this old man about six hours (not including drying time) do do three doors and the hatch, which was j u s t showing bubbles. A year later, nothing has progressed although I do realize the internal rust is still there. My HHR lives in a heated garage but it did not for the first ten years of its life. Michigan salt. I hate it.

 

There is a reason...

There is a sealer "supposedly" applied to the edge of the door skin right where it folds over and pinches onto the inner door structure. In most cases it was applied anywhere but the edge where it was supposed to be... A few pieces it actually ended up where it was supposed to go and those doors don't rust near as bad, if at all. Salt compounds the problem.

 

Uh, there was no Hem Sealer at Ramos during the time these were built. GM was putting it in elsewhere, but it hadn't gotten there at that point. Cobalt was the same. Cruze got it at Lordstown. It should cover the "hem" of the door, hood, hatch, etc., if it has it. It is a much cleaner look as well, but GM was still cheaping out at that point on small cars. I was processing the robots and conveyors.

Compare the HHR panel hems to something 10 years newer, and you will understand.

 

I don't miss the salted roads, for sure...

 

Michigan is the worst, too...

 

We get salt on secondary roads and brine on the main roads and highways