bed liner for frames

[mdg]

I was just wondering why I have not heard of people using the rhino or equivalant bed liner coating on frames. It seems that it would be a perfect coating as it would prevent rust, its durable, would provide more sound insulation from reaching the cab, comes in many colors and it has a life time warranty. I know they spray it under cabs for sound insulation and rust prevention. What do you guys think? anyone out there used it on their frames?

Thanks...Mark