I put 80,000 miles on the 07 I had with no rust living in the rust belt too.
The water it self is not that big of an enemy. Flushing with clean water is a good thing.

 

From looking at the pics it also does not look like it started inside the door. Pull the panel and look inside.

 

yeah, rust starts inside where its damp,and stays damp.if you never had a car rust away you will never understand! it an inside job!

 

Mine is washed once a week which is why I noticed it.

I don't think it really has anything to do with peoples cleaning habits of their H3's. You 08 drivers that don't have it should probably continue to check over the next few years as most of the ones showing it have 2 years on you.

They don't use sand mixed with our salt here, so the salt is laid on heavy. I assume that area stays wet if there is any precipitation because it sits below the door seal but ultimately it is most likey a production issue.

Good luck oiling the doors. I'm not sure how that would penetrate the pinch seam and prevent the issue in question but if it helps anyone sleep, it's worth the cost of the aerosol can.

I was considering using some POR on the area but, again, I don't think it's going to help inside that seam so it's is probably a waste of paint.

It's a shame that in 5 years or so we will see that nasty *** rust has eaten the bottom chuck of those doors. Much like the '91 chevy s10 I had. It had so many rust spots that the first day I moved to Arizona a little kid in the neighborhood rode up and asked "holy cow has your truck been shot?"

Maybe it will be time to make some tube doors by then.

 

in 55 yrs of driving dozens of veh,i can tell you that water gets in there and every veh i ever owned rusted away at the door bottoms. i remember glassing on bottom panels on all doors on a 74 econoline in the eighties.
both ford probes were showing rust there. a few pintos,oh yeah.
my 64 mercury,check.
my 92 crestline was best because it was a delux van and got special coating.

yes they ALL rust at the bottom eventually,some sooner than others

btw,water gets in by the window,cant stop it

 

I get how the water gets in there and I understand rust, I've had a 72 cutlass and currently have a 72 VW bus, what I meant is I don't understand how you are going to prevent those pinch seems from rusting by spraying anything in the door.

Maybe take the door panel off, coat the inside with a rubberized coating and the pinch seam as well but if its in there it's pointless.

 

It not from the water inside the door, it's seems to be from paint flaking off. The rear door of my 2010 H3 has paint flaking off in that exact area and it's starting to rust. There is a design/manufacturing issue of some sort. The paint just doesn't stick to the metal in that area very well for some reason.

I attached 3 pictures of my issue.

To give some background I have a 2010 H3. I'm from Minneapolis, MN so we do have salt on the road in the winters and such. All the pics are of the same door which is the rear drivers side door. The first 2 pictures is of the same rust spot. The pic H3_Rear_Rust_1 is a wider view and H3_Rear_Rust_2 is a close up. H3_Rear_Rust_3 is a new spot in the last weeks or so that the paint just pealed off and the metal is exposed.

 

Well the paint is bubbling because moisture is behind it.

jvorpahl - Does the bottom of your door have another layer of something on it? In the pics it looks textured like bedliner at the bottom. Aside from the bubbles

 

correctomundo!! thats why paint bubbles on wood,same thing!!

you can squeese,crush,smash two pieces of metal together,BUT you cannot keep vapors/fluids out. so spray some oily juice like ziebart used to do! oh where are you lee when we really need you.

lps displaces water,thats its fame and fortune.
if the choice is water or oil,hint,take the oil

 

My wifes -06 had the same issue, she drives a -08 Alpha now and there are no rust yet but I check it regularly keeping my fingers crossed that it will not show up on this one