Sorry dude, but the instant you stick that trailer in the brine, it's going to have a cancer you can't cure. A channel trailer will take a little longer to self destruct, if it's a tube trailer in six months you'll see it eating itself alive.
My first trailer, an EZ Loader tube type, took years to self destruct ...mainly from the inside out even tho I put fresh water thru it. Funny thing, it had a single HD axle
with brakes that had water hookup to flush the system out......it still corroded quick and I just all the mess off and never replaced them. Way back when I was a young kid, my oldest cousin did something I've never seen anyone do but him. He washed his axle down and backing plate well. Then he applied a heavy layer of regular grease on the entire axle, then wrapped burlap bag material over the whole axle, wired it up so it wouldn't come apart and applied another layer of grease over that. It helped !! I've seen people use a yard water sprinkler that sprays up and over, under their rig to rinse well. Good luck and be safe out there.