Im not certain what was used I would assume sand but that would be a guess. In regards to the primer it is a 2K epoxy primer from SPI. I have done some spot checking in various other areas of the cab and have not noted rust under the primer. I might go back to the location and see what the extent is. That being said if I moved on in the build I would always be nervous that rust would rear its ugly head eventually. I new I should have kept it with the old patine and let well enough alone.
Thanks,
Eric
