I've owned several salt water trailers. A painted one was left along side the road with the tag pulled, the id# had already rusted off.

The problems with springs is that the rub together and remove any coating. There are also little crevices between the u bolts, plates and bolts. The spray galvanize could trap salt water.

A liberal application of Ospho on the steel surfaces would help. Apply liberally and often. Put it in a spray bottle.

I've never tried the Salt A way, but it probably can't hurt.

A natural anti rust coating is a mix of pine tar, turpentine and linseed oil. Apply liberally on a hot day.

Start a sinking fund for trailer parts.

My Hobie 16 trailer is a 1978 E Z Loader. At the time it was the first galvanized trailer that B & E Marine in Michigan City, IN sold. It has never been in the water, fresh or salt. I have never felt the need to float the boat off. The 2000 Rocket trailer for the flats boat needs constant attention.