I found some stuff called Weathershed made by Cosmoline. $11 for a 13 oz can. Here is what it says

Provides long-term protection for farm implements, tools, boat shafts, propellers.
Withstands severe exposure to weather and salt-laden atmosphere
Lives up to name as world's best rust preventitive with two years of staying power


Tom

edited to correct Weathershield to Weathershed