Need advice on temporary rust treatment

Previous owner of my 74 welded diamond plate on top of the floorboards, creating a trough or gutter about 3/8" wide betweem the diamond plate and the sides of the tub. Water, snow, mud collects in this trough and - surprise- rust is forming on the inside of the tub. I don't want to tear the floorboards out for another year or two, when I plan to pull the tub and cherry it out. In the meantime I was going to treat it with Eastwood's rust converter and rust encapsulator paint, then put silicone caulk on top, filling in the trough. Anybody have a better idea? Thanks.