Preventing Rust on 2015 F150

I do a few different things. I fluid film every year. I use 3M cavity wax. I use white lithium grease for the heavy high traffic frame spots. I’ve used Cosmoline, I l Ike it, it turns into a durable wax like coating. I’ve used New Hampshire oil undercoating. There’s Krown. And a Woolwax (all similar to fluid film). And all would need to be done yearly...I actually do it twice a year.

CRC makes a “marine undercoating“ and it‘s similar to Consmoline, but cheaper.

And I’ve heard of this Noxudol recently, sounds like something that is maybe more permanent?

The real key is have to periodically check under there once every few months and do some undercoating touch ups to really keep it sealed and clean. IMO.