I had a very used trawler for 5 years and sprayed the shafts in the boat, copper tubing in engine room, house water pumps, through hull fittings, etc. with WD-40 and soon had to do it again and again.
Boeing apparently developed Boeshield T-9 for all sorts of sensitive aircraft corrosion protection. I spayed the same parts with T-9 in the trawler without any cleaning or scraping and never had to recoat them unless the T-9 had been rubbed off.
Now I use T-9 on my electric garage door rollers, boat trailer, etc. and my experience is that it lasts much longer than lithium grease or WD-40 and stops corrsion in its tracks.
I just bought a 12 pack box of the spay cans from Classic Motoring Accessories for $109.99. I have lots of toys to keep up like my new 2007 DV SC 2120 which I love and will protect with T-9. Pete