Author Topic: Undercoating and sandblasting  (Read 515 times)

Online Paul Tesone

  • Posts: 633
Undercoating and sandblasting
« on: January 03, 2018, 10:30:10 PM »
I'm starting a frame off restoration . The majority of the floor is gone and will need replacement sections welded in . The car has what appears to be factory or dealer applied undercoating that will interfere with the welding process . This is tough stuff that will not come off easily . I want it all removed - not just where the welding will take place . Will sandblasting do the job ? Can anyone recommend a sandblaster in the Boston area ? Thanks in advance . ... Paul Tesone CLC #6876

Offline Ralph Messina CLC 4937

  • Posts: 1113
    • CLC Member
      CLC Member #4937
Re: Undercoating and sandblasting
« Reply #1 on: January 03, 2018, 10:53:27 PM »
Hi Paul,

I've found the best way to remove undercoating s to heat it from the back side and scrape it off while warm. Sand blasting may work on the hard brittle type used in the 50's but it merely bounces off the later rubberized coating from the late 60's......What have you gotten yourself into now? Pictures please....

Ralph
1966 Fleetwood Brougham-with a new caretaker http://bit.ly/1GCn8I4
1966 Eldorado  http://bit.ly/1OrxLoY
2010 GMC Yukon

Offline 5390john

  • Posts: 91
    • CLC Member
      CLC Member #27391
  • Name: JAdams
Re: Undercoating and sandblasting
« Reply #2 on: January 03, 2018, 11:04:04 PM »
I had the exact same issue with my '55 CDV. I chose to have the body blasted with walnut shells. Almost all the undercoating was removed, but there are bits here and there that could not be reached.
 It worked reasonably well but the big problem was left over media in EVERY nook and cranny. It took forever to clean it all out and I'm not sure I'll ever get ALL of it.
If I had to do it over again I would most definitely have the body dipped, and I would strongly suggest you consider it over media blasting.
John Adams

Offline Mike Josephic CLC #3877

  • Posts: 1523
    • CLC Member
      CLC Member #3877
Re: Undercoating and sandblasting
« Reply #3 on: January 03, 2018, 11:32:07 PM »
Just curious -- what would you have the body
dipped into to remove old undercoating? 
What type of chemical was used?

When my car was done, it was done the old
fashioned way using heat, scraping and then
wiping with kerosene and solvents to remove
any last traces.  That did a great job but was,
as you may imagine, very labor intensive.

Mike
1955 Cadillac Eldorado
1973 Cadillac Eldorado
1995 Cadillac Seville
2004 Escalade
1997 GMC Suburban 4X4, 454 engine, 3/4 ton
custom built by Santa Fe in Evansville, IN
2011 Buick Lucerne CX
-------------------------------------
CLCMRC Museum Benefactor #38
Past: VP International Affiliates, Museum Board Director, President / Director Pittsburgh Region

Offline jackscad

  • Posts: 3
  • Name: Jack M. Ehoff
Re: Undercoating and sandblasting
« Reply #4 on: January 04, 2018, 12:17:59 AM »
Chemical dipping and media blasting both have a downside. I personally would rather be chasing out the blast residue then have to deal with the chemicals that will continue to leach out from seams and possibly cause paint problems later on.
Jack

Online Paul Tesone

  • Posts: 633
Re: Undercoating and sandblasting
« Reply #5 on: January 04, 2018, 12:35:13 AM »
 Hi Ralph - happy New Year . I'm still laughing at your question about what I'm getting into now . My wife and a couple of friends , as well as myself , have asked the same question . Well , about 25 years ago , I bought my 57 Biarritz which had its restoration completed a few years ago . At the time , the person I bought it from had a second 57 Biarritz that was not in such great condition . He convinced me to buy both cars , advising me that the second car would be needed as a parts car to restore the first one . As it turned out , during the restoration , I managed to buy all the parts I needed without touching the "parts car" . The parts car is in tough shape , but it is a complete , numbers matching , Dakota Red (love that color) car . So , I was left with a dilemma . What to do with the car . Parting it out was never a consideration . It was either sell it as is or restore it . Decided to restore it ( love that color ) . .. Now , as to condition : As noted above , the floors are gone ; rust in the expected places ( rockers , door bottoms , wheel wells ). The big surprise and disappointment was the discovery that the front cross member was badly cracked on the passenger side. Upon further inspection ( I never really examined the car until two weeks ago ),my restorer found that the driver's side had also been cracked and repaired at some point . I have since learned that this is a common problem with 57's and 58's .We decided to buy a replacement cross member . On the brighter side , if there is one ,the engine is not frozen and the pistons move easily when turning the fan ; and the transmission was full of fluid . Nonetheless , everything has to be rebuilt . So far , the bumpers and front quarters have been removed , as have the dash , seats , rear quarter stainless and trunk material . At this point ,we're still evaluating and working on a logical approach to the restoration . I think my restorer plans to replace the cross member and floors first . I'll post some pictures once we get the body off the frame . Any advice will be welcomed . Paul Tesone CLC # 6876 .       

Online Paul Tesone

  • Posts: 633
Re: Undercoating and sandblasting
« Reply #6 on: January 04, 2018, 12:51:09 AM »
 Jack - my restorer has the same opinion as you regarding future paint problems resulting from residual chemicals . He also has always had concerns about sheet metal distorting during blasting if done by an inexperienced person . As a result , when restoring my other cars , he removed the paint by hand with paint remover . He feels this project won't be as labor intensive as my other cars because there is only one layer of original paint . Time will tell . Thanks for the input . Paul Tesone CLC #6876 .

Offline Roger Zimmermann

  • Posts: 2317
  • Switzerland
    • CLC Member
      CLC Member #21015
  • Name: Roger Zimmermann
Re: Undercoating and sandblasting
« Reply #7 on: January 04, 2018, 04:55:28 AM »
There is a process using ...ice. As I'm not at home for some day, I cannot tell how this is done. A friend in Germany used that method to remove the undercoating of his Continenetal Mark II. The process however does not remove the rust not th paint.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham
1972 Coupe de Ville (not yet arrived)
2011 DTS
CLCMRC benefactor #101

Offline carguyblack

  • Posts: 580
  • Name: Chuck Dykstra
Re: Undercoating and sandblasting
« Reply #8 on: January 04, 2018, 08:42:25 AM »
My paint and body expert stays away from chemical dipping like the plague. Too many problems coming from seams and rolled over metal reappearing in the future. The fix often becomes worse than the problem. It may not show for a year or so, but it WILL show eventually.
My own experience with commercial blasting with the 50's undercoating is that the force causes heat on the metal which frequently just moved the melted coating around. Too much persistence and determination to get it off completely may end up warping some sensitive panels, if there are any under there.
I guess what I'm saying is that there was no perfect solution for me. Just be careful.
Chuck
Chuck Dykstra

1956 Sedan DeVille
1956 Coupe DeVille (2 sold)
1957 Oldsmobile 98 (sold)
1989 Bonneville SSE

Offline V63

  • Posts: 353
  • Name: W Link
Re: Undercoating and sandblasting
« Reply #9 on: January 04, 2018, 09:13:11 AM »
If time is on your side, automatic transmission fluid will soften undercoating evidenced by any car with a healthy ATF leak. I have used brake fluid as a quicker agent. Liquid Explosive products are commonly mentioned. not advised. Itís a messy job no mater what.

On the 53 eldo, as more of a survivor, it retained its hosed (typical) on emulsion since new. In this particular case  I noticed that the coating was uniformly adhering, no peeling or lifting anywhere. The way the emulsion was applied, it has a unique spray pattern in application. Hard to replicate, worth mention as repair areas would stand out if you are observing. This car has ZERO rust anywhere, ever. I was in every nook and cranny. I expected to find a little rust... OR evidence....just not the case.

 I pre-cleaned it all with a lye based cleaner and repainted the emulsion with a semi gloss black, some 15 spray cans. I feel this a better option as itís actually a black appearing finish than the brownish canned undercoating commonly used. Spray paint is a thinner product and it actually drys!

This was just an underside Ďfreshení up retaining the original under coating, no disassembly at all...save removing wheels and tires.

  I looked like a raccoon when done as I had on a respirator that didnít protect my upper face.

Couple before pics added too, stencil frame stamp retained. 
« Last Edit: January 04, 2018, 09:26:25 AM by V63 »

Offline signart

  • Posts: 195
Re: Undercoating and sandblasting
« Reply #10 on: January 04, 2018, 09:26:33 AM »
Really not that difficult using a propane torch or acetylene torch with the appropriate tip that spreads the flame (not a cutting torch), or a commercial heat gun. Apply just enough heat to the coating to soften it as you insert a sharp putty knife and remove the coating intact in large pieces. Keep the heat carefully regulated so not to melt the coating making a mess, just warming it enough to keep it together. Then finish with solvents for final clean up.
Blasting will remove the traces left over but makes it more difficult to remove coating with solvents after blasting.
Art D. Woody

Offline fishnjim

  • Posts: 388
    • CLC Member
      CLC Member #29423
  • Name: J. Bozin
Re: Undercoating and sandblasting
« Reply #11 on: January 04, 2018, 10:34:46 AM »
The "ice" that is used is dry ice (CO2).   I used that commercially for cleaning equipment.   Needs well ventilated (open) area - asphyxiation hazard.
Consider this.   Usually when the floor is "gone", it either sat on the ground(rusts from bottom up) or soaked up with water inside(top down).   Minor front pan damage if it came in through the cowl vents but may ruin unseen firewall sections.   That'll determine what kind of damage you're up against.   Sometimes undercoating is all that's holding it together, if top side.   Once you remove it, it falls apart even more.   Make sure you have a sound body structure before you take off the frame.   
I prefer to repair as much as possible before it comes off(less distortion) and goes to blasting.   You should seal after any surface treating, as rust starts immediately on active metal, and then you have to remove the sealer again to weld.
They also used tar sealers down in seams that blasting won't reach and it presents an equal challenge/fire hazard cutting/welding old sheet metal.   
Water media blasting claims to remove undercoat but I have no experience.   I don't like the thought of the mess it creates with all the glass media, so where it's done needs consideration.  You won't get any heat distortion.   
I would not dip a car that's not in real good condition or I can't get replacement panels for.   It sits in near boiling caustic for a day(just eats rust) or an acid bath which removes good metal, thinning sheet metal.   It's difficult enough to weld at original thickness.   If the panels are sound, metal loss won't matter that much as it needs no repair.   
ps: All media has to come out of the cracks anyway regardless of type or method, as if you don't, when you spray paint, it will come out but ruin your finish.   This is just one more step in the process, don't short cut.

Offline INTMD8

  • Posts: 753
Re: Undercoating and sandblasting
« Reply #12 on: January 04, 2018, 10:59:10 AM »
I have done this by heating with a torch, scraper and finish with a rag and kerosene.

Horrible job!

You will need to pay someone to do it but I would try this-

https://www.youtube.com/watch?v=pJTuCf5_Rho


Jim Moran.   1959 Series 62 Convertible

Offline 5390john

  • Posts: 91
    • CLC Member
      CLC Member #27391
  • Name: JAdams
Re: Undercoating and sandblasting
« Reply #13 on: January 04, 2018, 11:39:24 AM »
Here's a link to a local, Portland OR company, American Metal Cleaning.
www.americanmetalcleaning.com
These are the guys who do all the dipping for the TV show "Graveyard Carz" and they did some work for me on my '55 CDV (the dashboard frame). I think their process might be unique in that (their website says) it doesn't remove any metal, just rust.
My dash frame came out great, and if you watch Graveyard Carz, the rusty old Mopars come out pretty clean.
After going through the various comments posted on this thread, it all seems familiar to me. I had all the same questions and conclusions from when I was trying to make the decision of dip VS blast. My conclusion for my car was to blast with walnut shells. I reiterate that if I had to do it over again, I would go to American and have it dipped (voice of experience). One factoid to remember is that GM made Caddy's out of thicker metal than their other brands and that's an important consideration for selecting the process for rust and paint removal.
My guess is that there are other metal cleaning companies around the country that use a similar process to American's, would probably be worthwhile to research.
Just my $.02 worth.
John Adams
 

Offline G Pennington

  • Posts: 102
    • CLC Member
      CLC Member #17677
  • Name: G Pennington
Re: Undercoating and sandblasting
« Reply #14 on: January 04, 2018, 11:37:04 PM »
About 6 years ago, I had the main body section of my '53 convertible (and some other parts) chemically stripped (Ready-Strip type process).  It removed undercoating, grease, rust, and old paint completely.  After the final rinse, they blew out the seams, etc. with compressed air, and dried everything with a large heat gun. They then applied epoxy primer (PPG DPLF50) over everything, including window and top wells, hidden areas in trunk, etc.  Expensive, but very pleased with how it came out.  Now, six years later, the body is still in primer (plan to paint it when the weather warms up), and I see no rust popping up anywhere.
Unfortunately, the EPA shut the place down a few years ago, and I wound up having the fenders, doors, etc., media blasted.  The media blasting left some undercoating residue in the wheelwells but was easily cleaned up.
Gary Pennington
   1953 6267X CC
   1941 6267D CC

Offline tturley

  • Posts: 366
    • CLC Member
      CLC Member #28929
  • Name: Tom Turley
Re: Undercoating and sandblasting
« Reply #15 on: January 05, 2018, 01:22:49 AM »
I had a LaSalle water blasted and it worked well.no distortion what so ever and the water keeps the media under control. We did it on the driveway at the shop and cleanup was very easy.
Member # 28929
1940 Lasalle model 5019
2011 Escalade platinum Edition
1995 Ford F-150
2015 Buick Enclave

Offline Jay Friedman

  • Posts: 1667
    • CLC Member
      CLC Member #3210
Re: Undercoating and sandblasting
« Reply #16 on: January 05, 2018, 01:19:16 PM »
I have a question--maybe a dumb one--based on little knowledge of this sort of thing, as follows: After media blasting the frame, couldn't the residue of any media remaining in corners etc. be removed by steam cleaning?

This would be kind of like tturley's water blasting. 
« Last Edit: January 05, 2018, 04:54:11 PM by Jay Friedman »
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210
"If it won't work, get a bigger hammer."

Offline Roger Zimmermann

  • Posts: 2317
  • Switzerland
    • CLC Member
      CLC Member #21015
  • Name: Roger Zimmermann
Re: Undercoating and sandblasting
« Reply #17 on: January 06, 2018, 02:25:42 AM »
Jay, sand blasting is very efficient with many inconvenients as you probably know: warpage, sand which go everywere and stay as well the ability to rust almost instantly if not correctly protected. I have no experience with other blasting medias; it could be similar. On a fresh blasted steel part, if humidity is coming on it, rust will develop rather quickly.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham
1972 Coupe de Ville (not yet arrived)
2011 DTS
CLCMRC benefactor #101

Offline Jay Friedman

  • Posts: 1667
    • CLC Member
      CLC Member #3210
Re: Undercoating and sandblasting
« Reply #18 on: January 06, 2018, 01:03:04 PM »
Roger,  Thanks for the correction.  I was not sure it would work.  I mentioned the possibility because a friend who works for a large company with a fleet of trucks told me that they steam cleaned the underside of the trucks every so often to remove dirt.  I guess the frame of those trucks would not rust because of the residual oil and grease which remained. 
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210
"If it won't work, get a bigger hammer."

Offline P. Manoogian

  • CLC #29766
  • Posts: 234
  • Name: P.Manoogian
Re: Undercoating and sandblasting
« Reply #19 on: January 06, 2018, 07:49:50 PM »
Paul,


By now that undercoat must be dry. As such it should easily remove with Needle Scalers. I bought a large and a small at Harbor Freight and used them with great success to remove all undercoat from my 61 and my 70 AMX. It chips off quickly. Come by and you are welcome to borrow and bring to Scott so he can try them.


Peter


https://youtu.be/k84NehEbFEU


http://www.eastwood.com/rockwood-pistol-grip-needle-scaler.html?mrkgcl=764&mrkgadid={_mrkgadid}&rkg_id=h-851550d5c5772a3e5736ba0762977348_t-1515289766&SRCCODE=PLA00040&utm_medium=cpc&utm_source=bing&creative=10262021170&device=c&matchtype=e



« Last Edit: January 06, 2018, 07:52:52 PM by P. Manoogian »
1961 Eldorado - Shell Pearl/Mauve
1959 Coupe DeVille - Vegas Turquoise
2012 CTS Coupe- Crystal Red
1970 AMX