well I know some people have mentioned this before, but I think its worth mentioning again:

In my experience using rubberized undercoating (black spray cans, buy at autozone etc) is just a bad idea if you are in a rust prone area.

I applied the stuff to parts of my frame to "protect" it from rust. Well I noticed some rust under some of the coating this summer and scraped a bunch of it off and there was rust in areas that were clean before the application....so basically water can get under the stuff and when it does, and it will, rust will occur at a real fast rate.

My opinion is that people should stay away from the stuff.

pay the money for rust bullet or por 15, or do it the hard way and sand/wire brush and prime and paint.

just a heads up

 

yeah, i've been thinking to do something to mine, but i'm steering clear of the rubber stuff.

might as well pony up for the por15...

 

Clean away rust, spray w/ rust inbitive primer and/or paint, like Rustoleum then get some good undercoating like 3M or Crest and you'll be fine.

 

NTM rubberized undercoating melts easy....i get it all over the stuff inside my truck.....Its ok for most places tho, just be careful.

 

Years ago undercoating was the thing and all car dealers did there best to sell it to you before you left the lot. It wasn't to long before people got the idea that it was a big mistake. It only takes one small spot for water to get under it and it's really bad if you live here in the east where salted roads is the norm for winter ice control. When it starts in one spot it creates more and the rust is hard at work and you can't see it until it's to late. Stay away from any undercoating.
If you want to do it right have the frame blasted and start from scratch with the new Rust Olium products and touch up every year and it will be many years before you have any rust serious problems again, Mike

 

Back in 93-94 i had my 87 toy truck and that is when the spray in bed liners came out and i thought i would save some $$ and do it my self with that stuff. BIG MISTAKE! never dried and couldn't put anything in the bed of the truck. I ended up selling it like a month later.

 

Previous owner rubberized the all over the undercarriage - now it's all peeling off revealing a nice layer of rust. I'll never use the stuff...

 

I agree that the rattle can rubberized antirust products are of dubious value particularly if one applys them to an older vehicle that has accumulated dirt and grime on the chassis. Applied on a clean new vehicle is best. However, those types of coatings are essentially a protectorant from rock chips and serve as sound deadening material. Any rust protection is incidental.

 

I'm an autobody tech by trade, and well, most of you are off at least a little...

I'll address a few things:

If you have rust crawling under the undercoating, the factory coating was already broken, and likely already rusting when you coated it. If the undercoating was not there, the rust would be crawling under the paint instead. If the undercoating was applied to an unbroken, uncorroded, and painted or E-coated (as in the frame) surface, the undercoating can do no harm, it will only help. Cheap crap may just fall off and become useless, but it won't cause harm in the process.

Perhaps, but for how long? Any spray bomb primer will be inferior to professional catalyzed primers. The commercial quality stuff may stick to the metal, but the pro stuff chemically etches and bonds to the metal.

This is exactly the point - stopping rust before it starts. Seriously, no common road debris will penetrate the factory underbody coatings. This is the stuff that is applied to the underbody and lower body (that texture on the rocker panels, etc.) that I'm talking about here. It takes a pretty serious scrape, nick, gouge, or impact to penetrate it. At that point, sure - corrosion will start, but this is preferable to every stone that hits the vehicle starting hundreds of small rust spots. Look at cars in a parking lot some time. Look at the front bumpers and hoods and see how blasted they are. Then look at the rockers or any place where you see texture under the paint. My friend has a 1985 MR2 that was undercoated very early in its life, and the underbody is flawless. If you know these cars (and any pre-1990 Toyota) you know they're rust magnets.

The rust issues with our Toyota trucks stem from the poor factory finish on the frame and chasse components (anything black under the truck). I looked under a 2005 Tacoma a couple weeks ago, and sure enough - it was starting to rust in all the places you would expect - particularly the welds! Unfortunately, this is not unintentional - Car manufacturers want you as a customer again someday!

 

Old thread, but what if you cleaned the frame all up and primed it then used rubber undercoating?

 

It has already been said that if your prep, then prime or paint, then undercoat..you will be fine.

 

yeah, i did one side without priming kuz i had none but i primed the other side first. its just for this year if i like the truck ill take the bed off and do it all right next year

 

You sound like me. I am glad he posted that... cuz did my front end and not the back...I have been considering that next winter (when it is good cool weather) i am gonna do a body pull and completely refinish the frame and suspension.

Rather than undercoat it in the mean time i will keep it bare metal. I don't want the surface rust getting any worse in the meantime.

 

Yeah haha i just bought the truck last weekend for $500. its gonna be my winter beater and work truck. I got an Evo 8 that i dont drive in the winter and i wanna sell my 2000 cherokee now that i got the truck.