Read above. Sounds like they're using salt again.
But ya for rust prevention. I don't want to be one of those guys laying on my back, grinding away on rust 5 years from now and using por15 over it. I'd rather have it undercoated. Or use por15 now. I'll ask for the proper under coating in another thread.
Oh, I didn't realize that! In that case, I wouldn't even be driving in the Winter, haha!
Salt is my enemy!