I used to clean, grease and wrap my springs in Denso tape until I had occasion to remove said Denso tape. If water gets in it stays trapped in and causes severe corrosion of the spring. My springs are now naked and oiled.

I have found over the years that spraying or brushing deodorised Fish oil onto exposed ,rust prone and hard to paint areas (not the cosmetic areas) of the underbody (including springs) effectively prevents any further rusting. it stays sticky for a few weeks ,but then can be painted over. I have had the book Rust and rot for many years and find it useful but it dosnt mention anything about Fish oil. It will make a new car last forever if you apply it inside all body cavities and seams. Do people use it in the U K ?