I checked with the local truck accessory store and they apply Wool Wax (like Fluid Film but thicker) there and they told me that Wool Wax doesn't play well with the coating that GM applies to the frames of the full size trucks. They said to come back in 5 years after GMs frame coating has dried out and then have it applied.
Here's a few pics of the frame on my 2008 Silverado with 61k miles on it. I don't have any pictures but the cab mounts on the drivers side are just about gone too. The wax coating totally failed. I should have been checking it over the years but I had a 99 Silverado for 10+ years and the frame with the wax coating was in good shape when I got rid of it so I didn't bother to take a good close look at the 08's frame until the shock mount broke off.
I have a used frame for the 08 that I sandblasted and painted and plan on swapping it next year... That is if I don't get tired of looking at it and throw it on Craigs List first
Left upper shock mount, or where it use to be
Gas tank crossmember.. The bracket that held the gas tank strap rotted away and the tank is being held in by one strap
Left leaf spring front mount
Right side shock mount
Truck with 61k miles on it not showing any signs of rust.
bed of the truck with no rust on it.