Member Kelp posted this thread not long ago about rust at the cut locations of his Sprinter:
https://www.sportsmobileforum.com/fo...ust-19171.html
I finally had the opportunity to spend some time with this, here are some examples of what I found on my 2016 SMB Texas Sprinter:
It is interesting to note that every location was different and that the worst I saw was from the single screw penetrations. I made it a point to treat each of these small diameter penetrations as best I could, including dipping the screw into POR-15 just prior to reinserting it.
I used a combination of silicone, butyl tape, sandpaper and POR-15 to make my repairs. Each penetration had to be looked at individually and each treated a bit differently based on condition and access.
Here is a treated example, the large opening cut-out for the shore power plug.
Thanks to member Kelp for calling this to my/our attention. It deserves looking at.