Curious, since FMJ doesn't do well in the water, could I use oil-based polyurethane to seal my water traps against rust? Looking for longer wear than paint.

Try it and see.

if your buying something.
Why not just buy something that made for traps ?

What's water suitable to go over dip?

I doubt polyurethane would last any longer than paint. In fact paint may last longer since there are more solids in it.

I used a krylon flat camouflage green paint on my #5’s I have yet to see how it holds up but the only place I’m concerned about is where the levers ride up the jaws.

Maybe the answer for me is to have extra traps prepped and ready that can go in the “rotation” when some need maintenance.

Just use acrylic latex paint. I have been using It for years and It works just fine for traps being used In the water. 2 gallons of water mixed with one gallon of paint. Mix well during the dipping process.

Formula 1 from www.snareone.com but it’d be wise to ask them. Their # is on the site

Why add another dip over the first one? If you want a thicker coating just dry and dip again.

What's wrong with a little rust on your traps?

I know this is old-school, but it really works well. It wouldn't surprise me if a lot of new trappers have never tried it.

Get a uniform, light coat of rust on your traps, then boil in logwood crystals. Do it once every season or so and after a few years you will have a well seasoned trap. Kind of like seasoning a cast iron skillet; satisfying.

The old timers did not blue their guns they browned them. I did that with my first black powder kit. I used a degreaser then let the metal rust then I removed as much of that surface rust as I could with the degreaser. Then I let It rust some more. Eventually the metal had a coating of hard rust. AS long as you kept it oiled It was as good as blue job.

^^^^
Exactly, iron oxide can act as a protective barrier.

I prefer the hard slick dye job you get from using alder bark or walnut hulls over the powdery look of a logwood dye, but it shouldn't make a difference. I'm with waggler, old school works and I never have a problem with rust on my water traps boiling and dyeing them with bark or hulls. I also wax my footholds, and do it the old school way of just melting the wax on top of the water I am dyeing them in. If you leave your traps in there for a while they are the same temperature as the water and I've never had a problem with the wax flaking or being loose like some claim, and it saves a step.

I did Full metal jacket some new, shiny wolf traps one year, but putting multiple coats on to get the thickness desired I thought was more headache than waxing, and would just wax any new land traps I was going to cover when setting.

Another tip, to get an even coat of rust on new traps like waggler mentions, boil the oil off them then put them in a tote with water and vinegar, this will cause them to develop a light coat of rust faster. Interestingly enough, you can also use vinegar to remove heavy, flaking rust off of old neglected traps.