I like Chassis Saver (magnetpaint.com)

 

I set the power washer to very high pressure and the factory crap came right off. Line-X will then coat it for $129.00, and it is warrantied to not come off. I just used a rattle can black on mine, but might spring for the line-x eventually.

 

Yeah, I coat with simple green or Grease lightning and let soak, scrubbing where I can. Then I spray all the underside with Tire Shine. I like the armour All brand Xtreme shine. The only thing is that dust collects the first time you hit the gravel and you have to do it again. Pretty much it stays clean until the truck needs cleaning again...once a week...

 

I got this stuff from work it,s called CRC INDUSTRIAL SP-400 CORROSION INHIBITOR. They use this light amberish film spray to hit a bolt or anything under there to keep it from rusting out. Comes in a spraycan 10 oz. I did underneath my truck in 3 or 4 spots just to see a year and a half ago its still there. It said on the can spray last 2 years, so we'll see.

 

I think WD-40 works better than Armor All. WD-40 looks good and protects the metal.
Under coating and paint looks good too! Been there done that! But only lasts till it gets dirty again.
I once painted my whole frame and axels. Looked good for a while if you wash and scrub the frame and axels every time you wash the truck!
WD-40 quick and easy! Just hose off the frame while you wash, let dry then spray the frame with WD. No rubbing no buffing!

 

Clean your frame real good and spray some RustOleum gloss black on it and be done, thats what I do

 

double posted somehow?

 

Yeah, tried that. Dish soap, simple green, super clean (purple stuff), hot water pressure washer.

It's like trying to disolve a candle with dish soap, not happening.

The frame looked really rusty, but unless it is through rusted, the wax is still there. Don't ask me how, but with the amount of rust on the frame, there was a lot of wax too! You can see pics of the frame in my gallery from when I had the accident. I had to scrape, sand etc almost all that "looks" rusty to get it to clean metal.

 

I read somewhere that moisture can get under some coatings and trap the moisture. Dont have that problem in Southern California. It was to hot today!

 

I just use Rustoleum Semi-Flat... My diffs, leafs and small parts of the framerails. Lasts a couple years, and I pressure wash under my truck after wheeling every time, and occasionally before washes. Looks great, no rust peeking through, even after lots of snow/salt in Colorado and Utah this year, although I did pull the wheels and tires and pressure wash all the salt off when I got home.... if I ever sell this truck it will look like it has never been wheeled!

 

The secret here is, like all other painting, is the prep.

Get it as clean as possible and don't be afraid to use a wire wheel, emory cloth, or even sandpaper to get the surface ready. You can cut the wax-based undercaoting with Eastwood's undercoating remover or most prep solvents.

Once clean, there are a number of options. We typically use either the rattle cans of undercoating or rattle cans of gloss black for touch up, bulk and paint gun for the the entire frame. Gloss tends to look better and is certainly easier to clean. Bread bags or newspaper bags will help prevent painting your Bilsteins black.

POR-15 and Rust Bullet are also options, but they are significantly more money and require more involved application procedures.

As for the aloy metals and such, use Fluid Film but not WD-40. WD-40 is fishoil and it will penetrate the metal and cause a corrosive stain (this is especially true on aluminum, brass, and bronze)

As for the wheel wells, most any of the silicone based protectants (whatever is cheapest) will dress those up. We typically touch up the painted portions outside the plastic/rubber liners with the appropriate paint.

Be careful to apply whatever coating evenly to any of the drive shafts so as to keep them balanced.