2004 F-150 and newer cab corner rust

[batmantech]

This seems to be the normal thing on many. Have seen 2004 and even under warranty on a 2010 or 11.

Some people are replacing cab corners other just patching it.

Was wondering if everyone is seeing this. What actually causes it. Looks like they rust on the inside to out.

[Keith Browning]

Jeez! I have neve seen that

[forddieseldoctor]

Me either.

[Matt Saunoras]

We see the core support corners like that all the time but obviously not visible from the outside. 

[Aaron]

My buddy has done his brothers corners once and is getting ready to do his own. 05 an 07 trucks.

[8WA Sman]

Is the back window a slider? I have not ran across this on trucks this new but in the past when I have seen this it was from a rear window leak.