Rust protection

I've never used the product but, Fluid Film has good reviews on Amazon.
It comes in spray cans and larger containers.

Spray cans of liquid rubber. Or spray undercoat. Both readily available. Well maybe not in Kalifornia.

I second the idea of fluid film. I use it a lot under my truck and trailers. Works well.

I honestly do not think you can get any better than good old fashioned Rust-o-lium oil based paint (spray can or liquid). Any water based paint won't hold up on metal. But Rust-o-lium has always stood the test of time for me. It has a rust inhibitor and you can spray directly on the rust and it will kill it too.

I'm in the process of spray painting all the under carriage stuff on my travel trailer this year. I just sprayed my entry steps tonight and the exposed part of the main frame you can see behind the steps. I did the stablizer jacks and bumper and tongue last week. Black spray Rust-o-lium will protect for years and years. Nothing better in my opinion.

Waxoyl, BOESHIELD, or the traditional Cosmoline.

Wow..lots of options. Thanks

I just repainted my trailer tongue with Tremclad Professional spray paint in gloss black by Rust-oleum and am really pleased with the results ... dries in just 15 minutes so it's easy to get a lot of work done in a short period of time. I bought another can today for spraying the rest of the trailer frame. :B

Fluid Film will penetrate into areas that paint will not reach. It is easy to apply, taking little time, and can be sprayed on anything except inside the brakes. Trailers with leaf springs always have rust between the leaves and Fluid Film is especially beneficial for those. The only downsides are that it is messy when working on the sprayed components and it should be reapplied every year or so.

I use Fluid Film and it works well. Fluid Film penetrates the pores of the metal instead of just coating it. It lasts over a year for me, but I usually recoat once a year as part of annual maintenance. You can get it in spray or gallon cans. It's cheaper to brush or roll on the bulk of the job with the gallon can. The spray cans get pricey on big jobs. The spray cans are nice for those areas that the brush or roller can't reach. It's also good on things like locks and hinges.

You can also run it through an electric paint sprayer and spray it all on. I can run it through my sprayer without thinning and it's faster than brushing it on. For years I've pulled my trailer through the Salt Belt over the winter and most of the undercarriage still looks new.

The yellow zinc plated nuts & bolts under our TT started to rust after just one year. Our TT got delivered during a winter when there was lots of salt on the roads. Why can't dealers hose the underside down to remove road salt?? I replaced visible nuts & bolts on the elec. stab jacks with stainless steel. Still looks purdy after several seasons now. The plating they use (Chinese I assume) must be only only a couple of atom layers thick. :M Stainless steel isn't always stainless tho.

The frame and other painted things underneath is rusting in various spots. The powder coating layer they use also seems to be pretty thin (more like extremely thin). I also don't think they do a very good job of prepping the metal before powder coating. I need to get under the frame one of these days with some Rustoleum and do some touchup. Just can't get excited about the thought of working on my back over such a large area.