Severe rust damage on my Subaru Outback

I just discovered this today. When I opened the rear trunk of my Outback, I heard some weird grinding noise and upon inspection, I found lots of heavy rust and corrosion around where the door shuts. And the support arm that holds the back door open on the right side has caved in where it bolts to the car. Hard to explain but the pics should show clarify.

I don't know what's caused this. I suppose little drops of saltwater over time, but typically the kayaks are fairly dry when I load them up.
Has anyone seen anything like this? What might have caused it? Any ideas on how to fix it? It's structural damage so I'm afraid it could be fairly expensive.

Thanks in advance.
Andrew

Holy crap, do you live in a Pineapple under the sea?  Ya, that's going to be some serious coin to fix correctly.  How old is this vehicle?

2013. I just don't get it. I mean, occasionally when hoisting my Scupper Pro onto the boat a little salt water would trickle onto the hood, but not often and not in large quantities.
It's pretty foggy up where I am in SF, but then everyone would be having this issue.

Blame the neighborhood Andrew. The fog carries a ton of salt in it coming off the ocean and some cars are more susceptible to rust than others -- even from the same maker. I've had three different GTIs while living out here - two 2003's and now a 2011. So far only one has had significant rust damage, but it was toast by the time I got rid of it.

Brad

No expert, wrenched on lots of cars over the years.  Can't believe that was caused from the outside, not sure how it came from inside out but there's little if any protection on inside of body parts unless they're obviously going to be exposed to elements. Rocker panels, door panels, etc used to rust out but modern cars are generally protected on the inside of those areas as they learned about the issues.

Yikes! I doubt putting your kayak on the car caused this. Subarus are notorious for rusting, but I thought they changed coatings formulas in like 2006 to help prevent this.

Maybe check to see if there is any service bulletin/recall to try to soften the blow? 

I'm pretty sure you are correct that it was caused by saltwater dripping off your kayak combined with your environment.

I had the same thing happen with my 05 WRX but it started under the rubber on top of the windshield and eventually on a separate spot half way down the A piller which was worse but not as bad as your issue. I was pretty careful trying to avoid having salt water drip on it but it still happened. I am WAY MORE CAREFUL now with the replacement Subaru and spend MUCH time drying my kayak before loading.

Double check your warranty or recall notices.  My Tacoma paint just started peeling and I find out it's an ongoing problem for white toyotas.  I may have to fight them to get it covered.  All manner of toyotas are covered in an extended 15-year paint warranty fro the white 040 color but not Tacomas (Not enough complaints yet, they told me from Corporate.  Which I say is just bullshit)

Bushy

I hose down my car after every trip now because of this. the saltwater would also short my anti-thief and my horns would randomly go off

I say its salt water drops.  My van got rust bubbles due to salt water.

Even though i live in SJ i noticed that some parts of the roof of my 2012 subaru impreza had rust on it. I remember peeling some paint off and getting it down to the metal then putting touch up paint on it. I think these are from the rock chips that hit the roof then get exposed to the kayaks salt water. I also make sure my kayak is dry before i put it on my car but it's totally the kayak. It was never that bad tho.

Thanks for all the replies. The thing about saltwater dripping is that the Hobie is rarely wet when I load it. By the time I wheel it from the water to the car and then load the car, the boat is pretty dry. Any water inside runs out the drain plug onto the road.

Also, the corrosion is so consistent on both sides that it makes me wonder if it's the salt air.

Anyway, I don't know. If I can just not open the trunk anymore I'll be all good.

back in the day my brother bought a used Vega with rear hatch (similar) the car lived on the SD coast when he bought it, had similar issues all over, became a bondo sled when he was done.

someone above recommended rinsing with fresh water after each session - good advice, even better clean it if you can.  I've also started to wash/rinse my yak before I load it on the car, using the 123engineering (Paul) method of battery powered pressure washer, first with a 2L bottle of simple green solution, then about 5G of fresh water that I pack from home.

Salt water, amazing how much damage can happen in a short time. Salt water when dry, attracts moisture.

I have some pretty serious rust holes on my pick-up roof mostly near the gutters and on my lumber rack from saltwater. I don't rinse the truck after saltwater trips and it shows. Fortunately it has over 200,000 on it and still runs. unfortunately I think rain leaks through those holes and it smells pretty dank in the winter. Good-luck bro.