removing 45 yr old undercoating

[Ryan.C]

looking for the best method to remove factory undercoating and surface rust from the bottom of my '69.
I do plan to shoot the bottom with epoxy and rubberized undercoating.

[72Charger-SE]

Order 10 large pizzas & three cases of sodas...  have drills with wire wheels, steel brushes & safety glasses readily available...  Invite the teenager group over from your local church...  Give them an assignment and teach them about older cars... 

Sadly... there is no easy way that i found... ALOT... ALOT of hard work and manual labor...  elbow grease...  wire wheels & time... 
We (brother in law & I) built a rotisserie that made things a little easier...  I was able to get to all the areas... 

It took quite a bit of time to get it all done.   Hopefully someone else has the 'EASY BUTTON' solution...

[JB400]

I'll get back with you on this, this evening.  I soaked some parts with some penetrant a couple days ago while I was doing the same thing.  Just after sitting for 5 minutes, the undercoating come off a lot easier.  Curious as to how easy it comes off after soaking a couple days.

[Ghoste]

Heat can help sometimes too.

[tsmithae]

Heat can help sometimes too.

Heat and a scraper are the best that I have found so far.

[cdr]

A steam cleaner works great.but they are pricey to rent one.

[Canadian1968]

A wire wheel will work alright, but this very messy!! You will have undercoat everywhere!

There is no real easy to do.  The method I use was - for larger areas use a propane torch heat up area for a couple seconds and then scrape with putty knife . This is pretty effective and easy, smaller areas I used a flat screw driver . After I removed as much as I can with the heat, I then went the wire wheel or paint thinner / mineral spirits .

No real easy if you can't send it out to be blasted!

[B5 Charger]

   Get one of those plumbers propane torches and put a little heat on the undercoating.  It will soften up and you can use a putty knife to scrape it right off.  I've done this on several areas of my Charger.

[Ryan.C]

THANKS GUYS,

I think ill go the wire wheel route for the surface rust and propane torch for the undercoat.

funny story, my buddy just told me a local repair shop wants to charge him $900 for a wheel bearing and brake job. so I says lets make a deal, you buy the parts and ill fix your jalopy if you wire wheel the underside of my car. 

[B5 Charger]

These 3M discs are real quick for stripping paint and rust from metal.  I've used several.  They make them to fit an angle grinder and to chuck in a drill.  Awesome product and available at most box stores with a hardware section.

//http://3mcollision.com/3m-sandblaster-clean-n-strip-disc-54767.html

[Ryan.C]

These 3M discs are real quick for stripping paint and rust from metal.  I've used several.  They make them to fit an angle grinder and to chuck in a drill.  Awesome product and available at most box stores with a hardware section.

//http://3mcollision.com/3m-sandblaster-clean-n-strip-disc-54767.html

ill look into it thanks

[Mike DC]

 
Just buy a car so rusty that you have to cut off & replace the lower half of the unibody.  Problem solved. 

[JB400]

Here's how I've been removing the undercoating.  The victim is the passenger side splash guard.  

The first pic is with it with the top part soaking in PB parts blaster for 2 days. ( I meant to do this after 1 day, but wasn't able to get to it).  Center part is where I already scraped on it and removed the undercoating.  Bottom part is what it looked like before I started.

2nd pic, I sprayed the whole thing to just freshen up and break loose the undercoating.

3rd pic, is with the top part scraped clean after letting it sit for approx. 5 minutes.  It took about 5 min. to remove everything, spray it again with PB, and wipe it off clean.  It didn't take that much effort to remove the undercoating.  Matter of fact, it come off in large pieces.

4th pic is with the bottom part scraped clean as well and wiped.  It took quite a little bit more effort to remove the undercoating, but not nearly as much as it would without the PB.

Everything left on the splash guard is some surface rust.  

I say it'd probably be best to let it soak overnight, and then spray it again and let sit for 5-10 minutes then scrape away.
Best thing is, the only part of me that got dirty was my hands. I doubt you could say the same thing using a wire wheel.

[Ryan.C]

These 3M discs are real quick for stripping paint and rust from metal.  I've used several.  They make them to fit an angle grinder and to chuck in a drill.  Awesome product and available at most box stores with a hardware section.

//http://3mcollision.com/3m-sandblaster-clean-n-strip-disc-54767.html

These stripper discs make short work of under car crud. 7hrs labor and its almost done. I will still have to use a wire wheel/brush to get the really tight spots.
Thanks for the tip 

[Ryan.C]

the tools

[B5 Charger]

No problem!  Definitely one of my go to tools.  When I first bought one I didn't think it was going to do much but I was really surprised how well and how fast they work.   

[Ryan.C]

Just curious what is the "factory correct" way to prepare the undercar? I have heard the factory just primered the bottom and overspray is the only paint it got.
so what is the story?

[Troy]

I was going to say that the 3M discs are not great at removing sticky undercoating because they gum up  but I see you had them on a high speed die grinder so it probably helped them clear. For future reference...

* A "knotted" wire wheel on a 4" or 5" grinder works awesome. Very messy!!! It does melt some of the undercoating but clears extremely well. Can't get into really tight areas.
* Heat. I've used a heat gun and a scraper. Others use a torch - but you're a lot more likely to catch it on fire.
* Ice. A little unconventional but putting dry ice on your floor boards will harden the undercoating so much that it cracks and falls off when you bang on the metal. Obviously it does the same thing to your skin so be careful!
* On flat panels I've been using a cheap powered scraper/sander from Harbor Freight. Very fast. Doesn't do sharp curves or edges very well.
* Kerosene. Makes an incredible mess but doesn't go airborne like anything on a high speed wheel.

A combination of the above will probably give the best results.

For money, the local soda/plastic blaster will do it when they blast the car. In the future, I believe I will save myself lots of time, effort, and potentially unhealthy side effects and just pay them to do it. They claim they have a "solution" that makes quick work of it. I'm guessing kerosene and a high pressure, heated power washer. The environmental impact is probably high. I don't currently have a tow vehicle (but I do have a rotisserie) so transportation is an issue.

Troy