A bit of an update...
I stopped in to my usual body shop yesterday afternoon (where I had my accident damage repaired a few years back and where I had the light surface rust repainted on the underside of my rockers. The body place said if it’s rusting the way it is, the best thing to do is get it cut out and a new clean piece of metal welded back in for $500-700 (bodywork costs a lot here, at least it does here where I am in Canada...). The guy at the shop described it as moisture getting in between the two panels from behind (in my case, at least) and it’s not really an area that most shops rustproof well other than undercoating the wheel well as they’d have to drill holes to squirt undercoating in. He also said that because the inside of that panel has NVH foam, the foam basically holds any moisture in place in there once it gets in there. I tried wiping some dirt off the inside of the fender with a rag last night and feeling around after I got home...I have that waxy undercoating stuff that hardens, so I was feeling bumps, but I don’t know if that’s the feeling of rust bubbles coming through on the back or just some of the undercoating. The bubbles are on the usual wheel well spot right where where the inner panel of the fender well meets the outer panel of the body, so nobody can really get inside them unless I/they drilled a hole from in behind the taillight or something and then sprayed some into the panel with that wand thing they use...not sure if that is normal practice or not...? I guess my usual undercoating place doesn’t do it though...
Found this pic of a similar Accent to my car that shows the inner panels with the interior trim off, I can’t see why they couldn’t poke a hole behind a taillight and spray some of it down into the seams above the wheel-wells?
A grease trick the body guy told me to do was to slather the rust bubbles in a grease (I used white lithium grease as I have some at home) for the time being until I can get it repaired later this year when conditions are more favorable. MM54 and I both agree that probably doesn’t make a lot of sense if the bubbles are telling us it’s rusting from moisture getting in behind, but hey, guess I can try it.
I know my car is getting older (2009) and has 152,000kms on it now, but this is the first bit of real rust it’s gotten....sucks that it’ll cost this much to repair it, but I’ll save up and try and get it sorted when it’s warmer and drier later this year. Mechanically it’s got loads of life still left in it and the rest of the body is in great shape (as far as I know). If I can keep undercoating it yearly as I do and the rest stays OK, hopefully I can get a while out of it yet. The body guy said to do the grease trick, but I agree with you....I can’t see it doing much if the moisture is coming from behind. But...he suggested it, so no harm in trying I guess! :)
Blargh...rust sucks, especially when you don’t have a lot of money and you like your car a lot, even when it’s a cheap Korean ecobox...
...or at least 3 small rust bubbles worth of car cancer...152,000kms in salty Nova Scotian winter roads will tend to do that. Noticed them on the rear-right wheel arch this afternoon. This is the first body rust I’ve had. It’s a very small amount (my ugly fingertip for scale), so hopefully it won’t cost a ludicrous amount to fix:
Pardon all the salt on my car in the shots - I do get it undercoated every year, but I probably don’t wash it in the winter as often as I should. I’m hoping there’s nothing really nasty lurking back there and that it’s a simple grind back and repaint job. I can’t feel anything when I run my fingers on the lip inside the well, so I don’t think it’s bad. Getting it sorted now means I can nip it in the bud before it spreads! Hopefully I can get it looked at on Monday and get an appointment for next week.