When you have issues of corrosion on a vehicle, piece of equipment or anywhere else, try our Asset Preserver (AP). It goes on clear with a light tack (so you know it’s still working). Rainwater will not remove it, soap and water will. Unlike other so-called “earth-friendly” products, ours is actually biodegradable. It is also dielectric so it protects and enhances your electrical connections.
I’ve undercoated my own vehicles, 4 winters ago, where road salt is a major issue and the results have been excellent. Your skepticism is welcomed, try it for yourself.