I have used a product called Fluid Film on my daily driver for a few years now. I have a 300M that I spray the entire underbody with this stuff and it protects it perfectly from the salt and brine.
It would work for your issue, but one drawback. The product has an odd odor that people either like or hate. It is lanolin based, so to me it smells like sheered wool. I hate it for the first week or so after using, then get used to it. On a really hot day, the smell will come back.