Best way to clean underside?

[dspur]

I am scraping the undercoating off with a torch and scraper, and it peels off quite easily (finding some areas needing repair under it).

Once I get it all scraped off, what is the best way to clean the surface to eventually ready for paint. I am using steel brushes of every shape and size on air and battery tools.

What worked best for you? TIA

 

[R413]

Has anyone used dry ice blasting? I hear it works wonders on undercoating removal.

Another guy soaked the bottom of the car with gas, then used a heated pressure washer and it comes off clean.

I noticed if ATF soaked into the undercoat it comes off easily.

 

[Bird 426]

Solvent, mineral spirits. Undercoat is tar, a petroleum product.

 

[Davefinan]

You’re doing a nice smooth job of scraping. I have used industrial degreaser ( dont remember the brand) and TSP , both with great results. Pressure washing in between helps too.

 

[493 Mike]

I hand scraped the car in my avatar and then rubbed it off with gas and brush painted it with Rust Oleum black in 1981. It has held up well.
Mike

 

[matthon]

Goo Gone Automotive.

 

[dspur]

Has anyone used dry ice blasting? I hear it works wonders on undercoating removal.

Another guy soaked the bottom of the car with gas, then used a heated pressure washer and it comes off clean.

I noticed if ATF soaked into the undercoat it comes off easily.

It is on a lift in my shop. Unable to use a pressure washer and wheels / drive train out so cannot move it. Thx

 

[WileE]

Oohh... for a car. When I read "underside" I thought

 

[haywire 440]

I used a large blue tarp to cover the floor under the car. Bought the largest hard sided plastic kid pool to catch most of the wash water. The pool was on top of some plywood and had a set of Harbor Freight moving flat dollies underneath the plywood. I brought a garden hose into the shop for rinsing. A 5 gallon bucket with deluded Simple Green was applied with an extendable car wash hd brush to scrub off what was left of undercoating.

My undercoating was hard and mostly peeled off thankfully. It didn’t need heating.

With the dollies underneath the pool easily move side to side so it would be centered below the work area.

I imagine that if you use a flammable liquid the pool would handle that for awhile. A different brush might have to be used.

The pool was easy to empty after rolling it to the outside. Good luck.

I applied new undercoating as seen along the middle of the vehicle.