Now that I've got a touch of the salt, I'd like to do a little bay and lagoon fishing on my own. But I'm scared to drop the 19-year-old Triton bass boat into the salt (Jay said older Mercurys hold up the worst in salt, mines a Mariner). Plus it's a painted steel trailer and I think salt is a known killer of them.
I'm thinking of maybe picking up a welded jon for use on lake and occasional use at the coast. Maybe a galvanized or aluminum trailer. Any cons or other considerations from you with more experience?

If a John means flat bottom, I would highly consider a V or at least Semi V with very deep sides.

Just remember the bays can get real rough at times. A welded jon boat might beat you to death out there at times. Not sure what size you are looking for but blazer bay makes a solid bay boat for a reasonable price. They are located in Pensacola. The newer Mercury engines are fine for saltwater.

Wash it and flush the motor after every use. You'll be fine no more than you will go.

Kayak won't rust

Too much in there that will eat me for me to be in one of those.

I have had everything from a bass boat, to a welded jon, a Xpress H20B and now a Blazer Bay 2170. I still pick and choose my days with the BB. Not so much as I did when I was in my other boats but you still have to be smart about it.

I fish Mobile Bay and watch the weather out of a aluminum bass boat.

Agree with this. Fished the coast for many years out of a 20ft bass boat. Washed the boat, motor and trailer after every trip. Would normally pull the boat home and go run it that afternoon in a fresh water lake for a half hour or so.

You should be fine in the Triton.

And once that salt gets in your veins it's hard to go back to fresh.