November 20, 2021


Guest Author: @klaus_harold

Hey everyone! Happy Saturday to you all. Today we thought we would talk about how to protect our cruisers from road salt! The leaves have fallen and snow is already falling in many parts of the country. Snowy roads means the salt trucks are going to be coming back out soon enough. Road salt a Cruiser killer, salt equals rust for our old rigs; we should do everything we can to protect the steel cruiser bodies and parts from rusting away before our eyes. Inexpensive yearly maintenance by the application of some of the products we talk about below will save you thousands and thousands of dollars in rust repair work down the road.

There are many many products out there for water/salt/rust shielding, I've tried a few and also some home brew concoctions but have settled on two specifically which can work great in tandem.The two products I use for winterizing pre-treatment are Fluid Film and Cosmoline (Rust Veto 342). As with anything, they have their pro’s and con’s:

Fluid Film
  • Environmentally friendlier option.
  • Creeps and travels into pinch seams, will flow around to the back sides of things like fasteners and brake lines when you can only spray the front.
  • Less temperature/equipment sensitive to spray.
  • Will get washed off in areas subject to constant mud/water spray from tires (note that “washed off” merely by visual appearance can be deceiving, surfaces will often still bead water long after it appears to be gone).
  • Can effectively be applied to somewhat dirty surfaces, the FF will saturate the dust/dirt and stick to what’s underneath.
  • Will stay wet and dirty, getting all over your hands/clothes/tools during maintenance or repair work.
  • Can be rinsed with a hose to minimal effect.
  • Can be mostly power washed off (for spring cleaning; note that a very thin layer will usually remain on the surface).
Cosmoline (Rust Veto 342)
  • Needs a good clean surface to properly adhere (ideal for new vehicles, rebuilds, or after a good scrubbing).
  • Will last for many many years in areas like the bottom side of floor pans and pieces of frame and suspension not subjected to abrasive tire spray.
  • Unaffected by water and mud spray, but will eventually be eroded by gritty/sandy mud (i.e. high speed on muddy gravel roads).
  • Dries to a waxy coating that will not easily rub off during maintenance.
  • Solvent carrier may not be friendly to some rubber/plastic parts.
  • Can be power washed with no ill effects (ok, maybe if you had hot water and got close you could start to take it off… but a normal car wash, no).
  • Will melt again during use and entrap dirt on diffs, oil pans, etc. (making these appear “dirtier”).
  • Have a distinctive (some find offensive) odor
  • Seal off and protect painted, unpainted and lightly rusted surfaces.
  • Take some level of attention to maintain.
  • Are available in aerosol cans.
  • Are available in black color.

Now that you know about these two products (and other name brands of the same type), lets talk about how to get them under your rig!


Both can be applied with a standard “Shultz” type underbody gun, or with one of the fancier adjustable units from several vendors (one of these is necessary to use the 360 degree wand attachments). Both need to be room temp or above to apply, you can sit the pail/jug in a bucket of hot water to warm them up or keep them warm during application if it’s already cold out.

Getting ready to spray the Fluid Film

The 1 and 5 gallon pails of each are most economical, the cosmoline is easy to pour however fluid film is thixotropic and behaves more like pudding when you try and pour it into the relatively small 1 qt sprayer bottle openings. The easiest way I have found to fill them is to buy a package of 150ml or larger syringes (a few dollars each) and cut the tip off so you have a ¼” or larger hole on the end, then simply stick one down in the bucket, suck up some product, and squirt it out in the spray bottle. Tin foil can be used to wrap the exhaust or other areas you don't want to spray.

A fresh, clean vehicle should have cosmoline sprayed onto all the underbody chassis components, frame, axles, floor pans, backsides of bumpers etc.

Cosmoline applied to clean undercarriage

Fluid film should then be applied to any area that is not easily accessible. Body plugs in frame rails, door drains and sills, rocker panels, etc. should be removed and a 360 degree spray nozzle used to coat inside these areas, including the inside of all frame members and cross members. Most door drains will accept the small nozzle of the fluid film aerosol wand (i.e. from Kellsport) This is easiest done with all wheels including spare removed. I also go under the hood and coat just about everything except the exhaust. All brake lines, battery terminals, core support, AC lines, oil pans, exposed aluminum of engines, transmission cases, etc. Newer vehicles often need splash shields, wheel liners, etc. removed for best access. Other areas to pay attention to are the door and tailgate hinges (places that have friction amd exposed metal). I like to make sure the calipers/pins and parking brake mechanisms are coated good, but you don't want to get it into drum brakes. If you have some overspray on rotors, wipe it off with brake cleaner otherwise you will have no brakes until you burn it off (a couple hard pedal applications works, but it's probably best to keep it off friction surfaces). I also like to remove tail lights, turn signals, etc. in order to get inside body panels and at the back sides of seams and panels that aren't readily accessible. Common areas for rust on wagons (such as above the rear wheel arch) can be addressed by going through the rear interior panels and saturating the seams between the body panel and the wheel well. Make the inside lip on fenders is cleaned out well and coated good, this is an area that traps lots of gunk. Where I live it is not uncommon for pickups to be missing several inches of metal above the rear wheels before their owners have them paid off. This unnecessary damage can be avoided by understanding where dirt and salt gets trapped, cleaning it out and keeping it protected.

You can see the wet Fluid Film still creeping along the surfaces and protecting them.

During the winter my cleaning consists of rinsing off accumulated crud with a garden hose. That’s it. Come spring time, I power wash the underside and follow up with a rinse of Salt-A-Way to make myself feel better about driving out all possible residual salt trapped anywhere. After the first winter, if a vehicle has been properly coated with cosmoline it is not necessary to reapply it entirely. Look for any spots where it has abraded and touch them up. I do like to reapply fluid film in the nooks and crannies yearly though.

Depending on usage, both may need touch up during the winter season. This is made easy with aerosols cans.

You will notice dirt and dust accumulating on your freshly coated vehicle quite quickly if you drive on dusty or muddy roads, that’s OK. You have a layer of protection under it all. Don’t fret if your frame goes from a nice shiny black to a dirty brown. It’s gonna be that way forever now, but at least it won’t be rusty.

Despite the surface rust, these surfaces are covered and protected
Dirt accumulation on top of the coating can easily be cleaned off
Black Fluid Film sprayed on the undercarriage of a 60 series

Fluid film is also an excellent product for storage of tools, metal parts, firearms, or anything else made of metal that you'd like to protect. Once you start keeping it around you'll find many more uses for it.

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