I do not belive that is an issue. Leaf spring are heat treated thick steel, it would take a looong time for rust to compromise them. Your other components would be more likely to fail first. If the rust bothers you there are rust conversion products available, POR 15 is one. Wire brush and apply, it converts rust into a hard coating. I applied a type of rust converter to a 5th wheel frame and axles with a spray gun, turned out nice. Can't remember the brand, been a few years ago!
Here's one, 1 gallon was plenty for a 30' 5th wheel frame and axles-
https://www.google.com/shopping/prod...:1,prmr:1,cs:1