Do NOT do that unless you dont want any cab corners!! That stuff will hold all kinds of moisture,salt and crud.Honda use to use something similar on there quarter panals in the 80's and 90's and you might remember what the rear quaters looked like after a few yrs. Just get it oiled every year and you'll never have rust issues,take it from someone who live in the rust belt capital.

 

My cab corners were rusting out as well. Ford hasn't made replacement corners yet as body style is still too new. My local body shop cut out the corners, custom fabbed new corners and matched paint perfectly - impossible to even tell they've been replaced. He drilled a hole a few inches up so I could hit it with some rustproofing spray every few months, and so any moisture in there can dry out. Cost me $500.

 

my rockers are starting to show a little rust on my 06 with 100k miles.

 

I have an 07, around the bottom of the gas door is starting to rust, and the bottom of the front doors is rusting. The gas door is typical from what I have heard and seen, the doors are my own personal hell I think.

 

I have an 08 I purchased back in October 2011. Body appeared to be mint and only had 35k on it. Paint is starting to bubble on the cab on drivers side rear door in the area of the paint transition (gloss paint to textured paint). Needless to say I am PO'ed! Just traded in a Jeep that had the same problem due to excess foam being sprayed up into the wheel well by the OEM.
I did put a magnet on the area to see if it was a repair but it appears to be all metal. No sign of teh truck being a repaint. CARFAX looked fairly normal (nothing reported). Is this common for these vehicles?

 

I've owned numerous f150's and recently my 2010 was totally last August. I was looking for a used truck for months. Of course I went back to look at fords. That said to my dismay more then 50% of the used 04-10 f150's I looked at had paint peeling and bubbling issues. My personal 05 fx4 had paint peel issues the whole time I had it around the gas door, under the doors and Ford convinced me it was only my truck. Bs! All the used ones I looked at either had signs of begining issues or already had the same bubbling and peeling issues I had on my 05.
The common places I notice it is the drivers and passengers doors on the very bottom, under the gas door, the lower cab corners and above the rear wheels on the flared out section in the back upper corner. That said I gave up and said screw this. I bought a tundra and love it. Ford lost me after my family and me owning many many f150's, none of us do now due to these types of Ford issues being blamed on us. It's clearly not just our trucks.

 

definitely the truck mine does it at every gas station i go to

 

Got my replacement metal for my can corners today from ray buck auto body decent price less than 100 bucks and thick too