It's not for road salt protection (might help if you wash though) if that's what you mean, but it's not just for plastic.
https://www.amsoil.com/p/amsoil-mudslinger-mud-and-dirt-repellent-amssc/?zo=515729
Performance Features
• Provides a protective layer of armor against mud, dirt and snow.
• Eases clean-up after riding.
• RESTORES CLEANS AND SHINES PLASTIC FIBERGLASS AND
PAINTED SURFACES
• Provides a protective layer to counteract the damaging effects of UV rays