Put about a gallon of mineral spirits in a bucket. Throw in about a 1lb ground up paraffin and mix it with the mineral spirits.
It will take a few weeks to dissolve on its own, or you can use a cheap aquarium heater to heat the solution up to dissolve the wax. Once the wax is dissolved you add about a quart of light non-detergent oil like SAE 30.
The way it works is the wax and oil stay in solution (mineral spirits) which makes it easy to spray in every nook and cranny. Once sprayed the mineral spirits evaporates and leaves a oily/waxy covering over the surface.
If you scratch the wax, the oil from the wax around it will creep into the crack and protect it.
I've sprayed this on the underside of just about every vehicle I've owned.
So far, it seems to work well. We get some fairly snowy winters around here and they always overkill on the salt/brine. I also go to the Jersey shore where it is possible to drive on some of the beaches to fish (mostly Brigantine). I have not had rust problems more than the usual over the years.
From what I understand the recipe has been around for a long time and is regarded as homemade waxoyl.
Then again, I don't normally make a habit of driving directly
in the salt water. I was parked there for a while as the tide was on it's way in. Wife took the pic before we left
