This aka PNW Fishermans Friend.
It really works, I can attest to that, they make a couple of different Rust Reformer products, just make sure it's V2100.
V2100 System Rust Reformer Spray
Technical Data Sheet
Rust-OleumŪ High Performance Rust ReformerŪ is a specially
formulated coating containing a silane additive which is
capable of reacting with iron oxide in the rusted steel
reacted with iron oxide the desiccant action of the silane helps
inhibits further oxidation. Rust Reformer is for use on sound
surfaces and is not intended for use on clean metal
or galvanized steel. The material dries to a hard black finish. A
top coat is optional. Use when temperature is above 35°F (2°C)
and humidity is below 85% to ensure proper drying. Surface temperature must bebetween 35-100°F (2-38°C).