Trying not to waste money

I need to convert or halt Rust And then paint.

What's the most economical product???

Is it small enough to soak in white vinegar?

Hahaha no

it's 5' x10 trailer

I'm no help then.

I have used a couple of rust stop items in spray cans and they have worked for me , little spendy but will use it again

maybe use a spray bottle of white vinegar . . . ?

Napa had a product, not sure if they still do, but it was ok, if you can do some sand blasting I think that might be the fastest, and cheapest to remove the rust then paint.

Loctite has a product called SF 754(used to be called Extend) that works very good at stopping rust. I've used it on a lot of exterior pipe and tanks at work. Is kind of pricey though.

On steel boats used in salt water we use Ospho or Coroseal followed with 2 part epoxy primer. Good luck

Ospho has worked good for me around the farm.

Coroseal with a brush or paint roller in tray for flat surfaces. Wire cup brush remove rough stuff first. Needle gun really bad spots. Air blow surface clear. Dab that Coroseal into tight spots ,corners too. 2 part epoxy primer,red oxide. Rust is job security on a ship.lol

Couple quarts of speed dip prepared and applied with a weed sprayer.

That’s what I use on my homemade cage traps. I actually set them on a big piece of plastic so I can collect and reuse the excess.

Arcticotter has the right idea, lol

On most steel things that rust I find paint barely slows rust without extensive prep, even then.....Lately been using my homemade, net/trap dip. Stops rust, for awhile, is black and drys quickly and not sticky. Traps, chains, netting, tools, etc.

Take unfibered asphalt foundation coat, dilute with paint thinners, gas would probably work too. use about a quart of asphalt to a gallon or so thinners, you can play with the ratio, it's basically trap dip. spray, brush, dip whatever works for you...

I used spray cans of Rustoleum on an old ladder stand and it has held up fine. May not be the cheapest alternative though.