I posted an earlier note asking how to protect a new vehicle from rust in the Northeast. I received some replies mentioning rustproofing and undercoating. I've always heard that undercoating is a scam. Has that thinking changed? Googling for undercoating yields two completely different opinions - it's an absolute must if you want a vehicle to last..... and absolutely do not do it, it will make rust worse!
What opinions do people here have? Have you rustproofed/udnercoated your vehicle? Are you satisfied? Would you do it again? What type of shop is the best to apply it?

pag04

bump

You are talking about a brand new vehicle that has not seen a salty winter before?

If so, then rustproofing/undercoating will help. The amount it will help will mostly depend on the quality of rustproofing and ability of the person installing the rustproofing.

The reason why people will say it will make it worse, is if you take a vehicle that has been rusting for 10 years, and then cover all the rust with a solid undercoating, the existing rust will grow under the undercoating and eventually you will be left with nothing but the undercoating. If you scrape all the rust off of a 10 year old vehicle, repaint the bare steal and then undercoat, it will help keep new rust from forming.

This gentleman has been fixing rust on his truck Nelsonmd's Build Thread

Rust converter converts Fe2O3 (Ferrous Oxide or Rust) to primer like dark finish. I use that on big suspension parts where I can't get to with brush wheel.

I found this online:
"How a Rust Converter Works in Theory

Rust converters are designed to neutralize existing rust as well as prevent it from advancing its damage. The active ingredient in most rust converters is Tannin, in the form of tannic acid. This tannic acid combines with the Iron Oxide to form a more stable compound called Iron Tannate, which is typically black in color compared to the reddish color of rust. Many commercial rust converters will include both a polymer to act as a protective layer, and an additional acidic compound designed to accelerate the chemical processes related to the tannic acids. One such acid, known as Phosphoric acid may also work as a rust converter itself, by reacting with the Iron oxide and converting it to black ferric phosphate. "

I hope this helps.

I gave up fighting it long ago , its a loseing battle , and I tryed everything. Those who don't have to deal with it will never have the privlige of the smell of the sweet salt air on summer mornings nor the pleasure of driving a new vehicle every 5-6 years . sucks to be them

Last fall i went under my 03 and 08 4Runners with POR15's products (marine clean, metal ready, and black under-coating). This stuff hold up REALLY WELL! You just have to be careful with it on a few things...mainly YOURSELF! You gotta wear gloves throughout the whole thing (the marine clean and metal ready will make yer skin feel like it's encased in a plastic-glaze if youre not careful, and the actual POR15 black stuff NEVER comes out of clothes, and takes quite a while to come out of skin!)

I did the OEM skidplates first. The 03's was in tough shape. No holes, but being in Massachusetts with the winters and icey roads we get, salt is used in abundance. Here's how the 03 came out after 2 coats of the stuff:







You dont have to sand or grind to shiney, bare, new metal either. You just have to get the loose stuff off. It even states you SHOULDNT get down to new metal as it "grabs" and "holds" onto better.

I plan on doing the entire undercarriage this summer.

I had good luck with POR15 for a while, but after few years rust came back lifting POR like a skin off the snake. The fix: no more expansive POR15, instead I do steel wire sanding of rusted spots followed by Rust Convertor and finally Bed Liner for middle and gas tank skid plates as well flat bottom surfaces of the frame and control arms. Bed Liner keeps steel protected from rock chips and salt from eating trough. Front skid plate I keep semi-gloss black for stock look and ease of cleaning.

Just my $ 0.02

This is a great thread. I live in the Northwest where we don't salt the roads. My 4Runner was previously owned in New York. I couldn't believe how bad it was under.

I went the route of taking it almost down to bare metal. I used my 4 1/2" angle grinder with a knotted wire wheel. It took quite some time getting the front and rear cleaned up. I pulled both bumpers, skid plates and the spare tire. I had considered POR-15 but ended up not doing that. Instead I used rattle cans of primer for two coats and two coats of semi-gloss. Mostly due to the fact that I cleaned down to bare metal.

Since I'm installing FJ coils, spacers and 5100's tomorrow, I'll get the other areas that I couldn't reach. You can check out my "Trailrazer build" thread in the 4th Gen section to see the before and after pictures. It was pretty bad.

As for smelling the salt air and such... I'm glad I won't have to clean up after a salty winter again. If I lived in the Northeast I'd probably be doing this clean up every couple years or doing an undercoating that was rust preventative. Luckily most of the rust was down low. The sides and bottom of the frame had no soft spots. I went through some PB Blaster to get screws out without twisting the heads off.

I'd also recommend regularly lowering your spare tire and keeping the cable system lubricated. It was almost impossible to get the spare tire out. There was a lot of corrosion and rust jamming it up.

Didn't someone here use chainsaw oil???

I remember inquiring why chainsaw oil was used...it was because it 'sticks'.

I don't think it'll stay on during winter trough snow, ice and road salt. Also I'd hate to see that end up in ground water.

True...but, here is the thread link...FYI.

She got a hot oil spray today!

Living in New England rust is a given so I consider rust an ongoing maintenance issue.

I use a product called "Ospho" which has phosphoric acid in it. Remove the scale, leave the surface rust and brush it on. It has surfactants added so that it wicks into every nook and cranny. Turns the rust into black, inert iron phosphate (ferric phosphate). Its no cure for the problem, just a great maintenance tool.

Rust on frames and major metal components usually starts out at the welds due to the local alteration of the chemical/electrical properties of the metal. (put a sharp bend in a common steel nail and set it outside for a bit; notice where the rust gets started)

Marine outfitter called Jamestown Distributers sells Ospho in various sizes. Its not cheap but it goes a long ways.

I have a bran new 4runner in NW.

Do i need to scuff the chassis with sand paper first and then apply the POR15 ?

What about Fluid film? do i need the same approach with FF?
is there any product that works for brand new cars and does not need scuffing ?
Thank you !

Good luck with either POR 15 or Fluid Film. Been down that road many years ago.
Both are "Forum Darlings" that are not good at all.
You will be reapplying FF at least once a year.
If you have that kind of time and diligence, go for FF.

New vehicle? No need to scuff frame.
Look into WoolWax if you are thinking of Fluid Film.
WaxOyl (2 parts) and Cosmoline are excellent.
Don't use black as if you try to resell, someone may think you are hiding rust.plus it makes things hard to identify. Clear/Amber is the way to go.

I did my 4R before I hit 250 miles and used Cosmoline this time.

I second the WoolWax or FluidFilm type of coatings. I'm planning on doing that DIY for my truck soon.

There's a few YouTube videos show that even after 5+ years in a salty northern climate, there's hardly any rust. Yes, it sucks to reapply twice a year, but it's really an investment on your vehicle.