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Posted by: r_towle Nov 4 2014, 07:45 AM

When prepping a car for sandblasting, what is the common thing to do with the aluminum tags in the front trunk and door pillar?

I suppose the second question would be do I acid dip the car or get it sandblasted?

Posted by: cn2800 Nov 4 2014, 07:59 AM

I very carefully drilled out the rivets for those tags (don't forget the Karmann tag on the driver's door hinge pillar) and will rivet them back in place once paint is complete.

I've contemplated dipping the body, but have ruled it out since there's no way to remove the hot air tubes from inside the longitudinals without major surgery. I've read here that they're foil-lined cardboard. I can't imagine they'd fare well in an acid bath.

Posted by: r_towle Nov 4 2014, 08:11 AM

Look for threads here, McMark just cut open the longs from the outside in that area and removed the heater tube.
Give you a nice way to get access to spray in an epoxy coating after the dip is completed, then put the tube back in and close it up.

I am torn about which way to go with stripping....not sure if I want to deal with the level of work to get paint back on all the nooks and crannies that an acid bath would remove.

Also, not sure I don't want to do that....cause it's a good thing to do once and do right.

Posted by: mepstein Nov 4 2014, 08:24 AM

I wouldn't acid dip. You'll never be able to protect the spot welded seams.

Posted by: rudedude Nov 4 2014, 08:32 AM

Seeing the damage done to a 356 from dapo that I am restoring I would never have a car acid dipped.

Posted by: r_towle Nov 4 2014, 08:33 AM

After 40 years, they are no longer protected anyways.

Posted by: stevegm Nov 4 2014, 08:36 AM

I researched this pretty well a while back, and spoke with a company in Charlotte that does the dipping. Unless the car if very rusted, they didn't think dipping was the way to go. My conclusion was that dipping was too risky and media blasting was a better solution. Just my .02 cents.

Posted by: altitude411 Nov 4 2014, 08:40 AM

Plastic bead media blasting is the way to go in my opinion. Very gentle on the metal (doesn't pit or stress) and more control over the amount of material removed. You can leave the seam sealer intact and the media is easily removed with air. Can be used on fiberglass without removing gel coat. This is what is used on aircraft aluminum.

Posted by: rgalla9146 Nov 4 2014, 03:19 PM

Carefully drill the two pop rivets under the front hood.
The paint/body tag on the drivers door pillar can be removed by pushing the rivets out with a lever arranged through the speaker recess.
Push them out slowly, each one a little at a time.
The rivets can even be re-used, or.... Stoddard sells them.
I'd blast it.
But tape and plug every opening or you'll have a pile of sand fall out every time you close a door.

Posted by: rick 918-S Nov 4 2014, 04:10 PM

http://www.914world.com/bbs2/index.php?showtopic=230343&hl=

I would cut the longs open and do this. The only welding you would do is replacing the outer, sill and triangles. You could use eastwood encapsolator to protect the inside of the weld area.

Posted by: balljoint Nov 4 2014, 04:29 PM

I get sand all over the dash every time I turn the fan on to defrost the windshield.

Posted by: SixerJ Nov 5 2014, 05:05 PM

Maybe useful background info, but unfortunately doesn't not resolve your personal dilemma

Acid dipping is big business in the UK and there are two well established companies with slightly different processes

http://www.surfaceprocessing.co.uk/for-cars.html

http://www.envirostripukltd.com/portfolio/auto-restoration

SPL have been going for years and years and have slowly improved the process and added steps, the final part being a modern ecoat which should help resolve the enclosed and hard to get to spaces which would be key for me personally. They have some potentially interesting info as to how to improve the dipping process - drilling small drain holes etc

Envirostip use an a kind of autoclave idea in the 1st instance to break paint, sealant etc down, then a much more expensive acid process to kill the rust (in comparison to SPL) which results in fewer issues later

I like the idea of Envirostip but not the fact you are left with an unprotected shell in cavities. They do etch prime, but that does not resolve the cavity issues

The blast verses dip camps are fairly polarised here

The results of long term dipping I should be able to post once I start work on my -6 as I spoke to the PO yesterday and he confirms it was dipped in the early 2000's. The closed compartments worry me as this was before the days of ecoat and protection will only be as good as getting the cavity gun in there. As she's was a race car I guess the heater tube issue did not matter

If you do decide to dip you must remove the alloy tags as apparently the acid will eat them for lunch

Posted by: r_towle Nov 5 2014, 05:37 PM

Interesting note, the initial dip is a BASE.

The acid dip, typically phosphoric acid, is down to neutralize the base and stop the process from continuing.
Phosphoric acid also helps stop rust from continuing...same reason.

Then wash it off with water...

So the car sits for a long time in a base solution, and is dipped pretty fast into an acid bath.

Now I want to go out and weigh a small piece of sheet metal and put it into phosphoric acid for a week to see what happens.

Rich

Posted by: lsintampa Nov 5 2014, 06:00 PM

I acid dipped....

Then por-15 the entire car...

Had to dip it twice - the first round we didn't get it cleaned in time and it started to rust again...

I've no experience with media blasting.

Acid takes it down to it's roots - that's for sure.

Sorry I don't have photos handy of the after-bath... but here's how it came out in the end.

Ended up selling it to a classic car dealer - his pro photos towards the end....

https://plus.google.com/photos/116912054149636297691/albums/5636393909343933585?authkey=CLGryuPK67yhzwE

Posted by: Mikey914 Nov 5 2014, 11:32 PM

I've used soda blasting to spot clean a few areas.

Posted by: SirAndy Nov 6 2014, 11:09 AM

Whatever you do, don't use sand to blast your car.



I found this more than 5 years later:

Posted by: lsintampa Nov 6 2014, 11:32 AM

Sand will get into everything, for sure. Ever go to the beach?

Anyway, the question sort of implies dealing with only the metal - as in the body and associated parts are void of all other parts, etc.

I've heard of shops that will media blast a "roller"...... IDK, IMHO when you get to the point of asking acid or media / I'd assume it's just body metal.

If the care is that far down to just body parts, it's just a matter of choice. Either process requires a lot of cleaning up afterward.

Posted by: r_towle Nov 6 2014, 06:30 PM

My plan, either way, is to strip it to the tub and bring it to a place on a dolly.
So it would just be a bare tub, which
I am not looking forward to....just cause it will create thousands of little projects...

Rich

Posted by: Katmanken Nov 6 2014, 06:31 PM

And you can do the electrolysis process on a whole car too. Place in Cincinnati called American Metal Refinishing that used that process to clean some fenders and a rear lid on my teener. Parts went in rusty and painted, and came back beautifully cleaned. They even knocked the rust out of the fold at the back of the rear lid. Parts were charged and lasted for more than 6 months without rusting. Watched them haul an old model T out of their inground pool and an engine block. Looked great. Looks like they are a chain with a few more places here and there.

Doesn't go between welded seams, but then nothing does.

Posted by: r_towle Nov 6 2014, 06:35 PM

I am starting to lean toward dipping the car, then sending it to a shop in Boston that Cevan found and have the whole thing galvanized.

I would not galvanize the removable panels, and depending upon what I find out, I may just sand off the top of the tub in prep for paint.....but then the underside and all the little nooks and crannies could be galvanized...

No idea what it might cost, but it won't hurt to investigate this.

Rich

Posted by: roblav1 Nov 7 2014, 12:59 AM

I just went through this. Aircraft stripper - let it sit for an hour - then hit it with a power washer. 4 gallons did the entire car (approx $40 per gallon) - inside and out. It IS A PAIN!


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Posted by: Phoenix-MN Nov 7 2014, 07:26 AM

This is how I did my chassis, years ago there was a shop in White Bear Lake that did this process. The chassis didn't flash rust at all and I worked on it for a whole summer before sealing it.

Posted by: CptTripps Nov 7 2014, 09:01 AM

+1 for http://www.redi-coat.com/

If I had to do it over again, this is what I'd do. For $2,700....that's well worth it in my opinion. Here's what I spent to get the car that far.

Media Blasting: $1,000
Epoxy Paint: $300
Stuff to coat inside of longs: $200

So I'm $1,500 into mine, and there is still likely surface rust hiding in nooks and crannies inside the longs and such.

RediCoat makes sure you have a 914 that is quite literally "rust free".

Posted by: boxsterfan Nov 7 2014, 04:33 PM

Take the floors out. There is rust in the seams. And if I'm doing a car, I'm cutting open the longs to get every inch I can in there.

Posted by: SixerJ Nov 8 2014, 03:25 AM

Quite possibly a stupid suggestion - why not cut open the longs, replace the heater tubes with steel tube / fixed with a silt down the tube & jubilee clips (like some exhausts). Then send it for its final bath and ecoating?

You now have a 914 that does not have to be messed about with post dipping

Also question for Rick / Scotty / pro body guys. Is there any special prep that has to be done to ecoat before paint? I have heard that primer does not adhere well to ecoat and you have to rub it all the way or a fair way down, that does not make sense to me as every automotive manufacture now uses ecoat and they are not going to do this. I could see you would have to key it up with scotch brite / DA etc but rubbing right down kind of defeats the whole idea of the protection - sorry for the hijack

Posted by: Jon H. Nov 8 2014, 08:45 AM

If you spray you high build primer on top of the epoxy within 48 hours you not need to sand the epoxy coat. Unless the epoxy coat is baked. This for Nason brand products. I'm sure other brands are similar.

Jon h.

Posted by: partwerks Nov 8 2014, 07:29 PM

Where exactly would need to be cut open to remove the heater tubes to address any possible rust issues?

Posted by: veekry9 Nov 8 2014, 08:13 PM

Redi-Strip.

http://www.redi-strip.com/

https://www.facebook.com/pages/Redi-Strip-Company/128612050544459

Many decades in the biz.
Phosphate post coating for rust inhibition.
A rare rusted 4130 airframe?
Yup.

http://www.nemgtr.org/index.php/members-home/tech-topics-list/231-redi-strip-revisited

http://www.jalopyjournal.com/forum/threads/redi-strip-in-pa.127217/

http://www.redistripindy.com/

The marketers of Vise-Grip also carries Cling-Surface,a prepared bath for rusted parts.
Cleans heavily varnished ferrous internal parts perfectly.

Posted by: veekry9 Nov 8 2014, 08:24 PM

Come to think of it,I haven't come across anyone here on the World who has demonstrated the naval jelly method of rust removal.
I used it recently to treat the seams of the hood where a line of corrosion peeped through the original paint.
A few gallons of the stuff works wonders on a very thorough level.

Posted by: Maltese Falcon Nov 8 2014, 09:57 PM

Had our current- build blasted with garnet sand. The media blast co. said that the 914 has the softest metal of all Porsches.
The grit + psi needs to be just right to avoid blasting damage.
Yes we are pulling sand out with vacuum cleaners + blowing it out too...but the unibody looks brand new, and welds like a dream !
Marty

Posted by: McMark Nov 9 2014, 10:47 AM

I think I would go this route if I were to dip another car.

Check out http://www.914world.com/bbs2/index.php?showtopic=28226 to see what you're heading for.

Posted by: r_towle May 15 2017, 10:27 PM

So, a few years have passed. What does everyone think about dipping versus media blasting?

My new plan is to send it out for blasting, metal work, then paint.
I don't have the time or energy anymore so I need to hire this work out.
I am going to strip the car, put in door braces....dolly or rotisserie depending upon how I choose to clean it. I am leaning towards media blasting it so I can leave the longs alone.

Wow, three of my go to mentors are gone
I need to get this car done.

Posted by: r_towle May 15 2017, 10:35 PM

Best/sad part of this is I was searching for any threads on this topic and I found my own thread, and I could not remember I ever asked this......ahhh

Posted by: McMark May 16 2017, 06:38 AM

Blasting for me.

Posted by: bulitt May 16 2017, 06:58 AM

Just use your abrasive personality?

Posted by: Perry Kiehl May 16 2017, 10:16 AM

If you have a really rusty shell, then dip it, but there's a lot of work in that.

If it's a solid car and you just want to have the exterior paint removed, then see if you can find someone who does soda blasting.

DIY chemical stripping is OK too but messy. I tape off all the seams so the stripper doesn't get in the jambs, etc. A few tips I've picked up on the aircraft stripper are: apply it with a single brush stroke and don't brush over it; once you get like a 1' x2" area coated, cover it with plastic film, this slows evaporation and forces the solvents into the surface. Cover the floors, wear gloves, eye and respiratory protection in a well ventilated area.

Posted by: rgalla9146 May 16 2017, 12:43 PM

Yes, yes,yes,yes and yes.
Also, do it on the hottest, sunniest day possible, outside.

Posted by: 6freak May 16 2017, 02:20 PM

with ice! look into that, it works good and no sand or HAZMAT to deal with

Posted by: amfab May 16 2017, 03:01 PM

I am curious about the reinforcement you did that ties the rear of the inner longs to the inner firewall. do you have a closeup of that?

Thanks

-Andrew

Posted by: jimkelly May 16 2017, 06:24 PM

the question i have about acid dip is that all paint will be removed but there is no way a normal paint job will get to all places an acid dip will leave bare. seems to me sand blast is bets option?

Posted by: bulitt May 17 2017, 07:40 AM

Rich: talk to Scotty. He has the dustless set up and mixes in a zinc solution to help with flash rust. Wonder what % of the abrasive gets washed away out of the nooks and crannies? But he could tell you.

Posted by: mepstein May 17 2017, 07:57 AM

Unfortunately, the dustless setup isnt all its cracked up to be.

Posted by: r_towle May 17 2017, 08:07 AM

I am not doing this project, I will sub contract it out.
That said, Scotty currently has a very long lead time.

I will need to get it stripped before I send it somewhere for the metal work to be completed, so my feelings today are media blasting and let Abel (my son) deal with the rust that happens down the road from the inside of cavities...

Rich

Posted by: cary May 17 2017, 08:20 AM

On Doug's project we went with soda blasting, rinsed with Hold Tight then sprayed with SPI epoxy primer. All of this was done on my rotisserie so it was real thorough. I dropped it off at the soda blasting shop and picked it up at the paint booth.

http://leonardsodablasting.com/?gclid=CjwKEAjw6e_IBRDvorfv2Ku79jMSJAAuiv9YbIBNR19ier816zhW4cZxTeS6alfwBKrNcyg-oiDJPRoC2uvw_wcB

http://www.holdtight.com/

You have to confirm with Doug, but I think it was right around $3k for everything.

Posted by: roblav1 Sep 2 2017, 06:21 PM

My old car is the white one in the rotisserie. I built it for a 993 engine. Unfortunately, I sold it in early 2015.

Someone asked about the diagonal sheet steel I welded into the rear corners. I stole the idea from early 911 Targas, where Porsche did something very similar. IMHO, after studying the chassis structure, I believe it will help quite a bit. I made them about 5-6" wide at the diagonal and bent at the top and bottom to get a good weld in shear. I was concerned with the seat not going all the way back, or I would have made them wider.

Anyway, I'm looking to do another 914 into a six. So if a decent chassis comes along, I'd be interested.

Thanks,

Rob

Posted by: mepstein Sep 2 2017, 07:44 PM

I've been thinking about this. the 911 chassis that we get media blasted come out ok but our metal guy still has to do a ton of work once we get them back. Cut out all the swiss cheese metal that was hidden with paint and bondo, remove a lot of the epoxy primer to do the metal work, ect.

Recently we sent out some tubs to an acid dipping co. and I'm waiting to see the results.

I know the paper heater tubes dissolve in the acid.

Here's my question. what if I replace those tubes with another one by snaking it through the openings on each end of the long. Similar to what is done with oil lines on a 6 conversion or water lines on a Suby. I know the lines will have a smaller ID than stock but they could be thin walled (no high pressure like an oil or water line) so maybe the ID is big enough. If I can get enough hot air through the tube, I wonder if a large, insulated tube is needed. Even the heat on my 4 cylinder car, without a working electric fan, is HOT in the winter and unlike my daily driver, I'm not driving my six on the coldest days of the year. I'm really just looking to stay warm on the >40 degree days.

Posted by: CptTripps Mar 23 2021, 09:37 AM

::: digging up an old topic, so I don't have to make a new one with the same question :::

Is the general consensus still that media blasting is the better option to dipping? Just checking to see if there's been a technology advancement or more opinions.

I called a few dipping places within a few hours of me, and got quotes from $3,000-$4,000 to dip a chassis.

Found a local place that media blasts, and got quoted under $500 for the tub if it's on a rotisserie.

Leaning towards blasting again, but looking for if someone found a better way to go about it.

Posted by: ClayPerrine Mar 23 2021, 09:47 AM

dipping will dissolve the paper tubes in the longs....

Media blasting will not.

And it is cheaper.

Clay

Posted by: Root_Werks Mar 23 2021, 10:02 AM

If you want to dip, prepare the body for it. I've only dipped two cars, both 356's and it's a DEAL to have done. Getting almost impossible to find a shop with a tub large enough and spend the time on a car body anymore. No money in it for them.

Bare body delivered and I mean bare
Little holes drilled to ensure air bubbles can escape
Dipped, wiggled around, turned over a few times (super cool to watch, friggen stinks though)

Then the hard part comes, gotta get all the acid off and out. I forget what solution is used, but they basically pressure wash the body for 3-4 hours. Tilt it, giggle it, wait, blast with air, pressure wash again etc. This is the longest part.

Then dip it in a phosphate solution = never rust again!

Had it done in Canada back in 2018 and it was roughly $12k US back then. Don't think the shop does car bodies anymore.

Posted by: mepstein Mar 23 2021, 10:07 AM

Plastic media blasting worked well for us when I worked at the shop.
There is no best method, just what’s best for you. They all have comprises.

We used a place called - plastic media blast, near philly pa.

Posted by: worn Mar 23 2021, 03:46 PM

Why is it either, or? The acid will get to the innards, the sand will be all over the place. Neither is very selective. If the box beams that make up the longs, tunnel, and fire wall have significant rust inside, then cutting them apart to restore strength makes sense. If they look bad but are not compromised, then there are coatings that will neutralize the rust and block off water to stop future decay.
It turns out that little British sports cars also rust a noted restorer has pointed out that these cars are no longer in the used car worthless category. They probably will not be parked forever in the rain or coated solid white with salt like my daily driver is right now. I have sand blasted frame and body and discovered that afterwards you never leave the Sahara. Can’t believe dipping is that much better. Strip, sand, convert if needed, epoxy to block H2O.

Posted by: Tdskip Mar 23 2021, 03:52 PM

In the UK they dip the cars post acid in a coating. You can also spray a huge amount of something like an Eastwood Internal Framecoating.

Posted by: Cairo94507 Mar 23 2021, 04:22 PM

I would do media blasting and ask the blaster what the best media is for the soft, old, potentially thin metal. Have it done by a pro and let him know your concerns. If possible, I would be there to watch it get done. Be sure to protect any chassis numbers or VIN tags.

Posted by: Tdskip Mar 23 2021, 05:09 PM

Soda blasting is a low risk option, itching to give it a try.

Posted by: ClayPerrine Mar 23 2021, 08:25 PM

Dry Ice... works as good as soda blasting, and it never leaves anything behind. Once it warms up, it evaporates.

Clay

Posted by: Luke M Mar 24 2021, 05:04 AM

This thread came up at the right time. I just met with a mobile blasting owner last week. He's going to blast both my brothers 914 and my 6 at the end of April. He came out to look at my 6 to get a good idea on what he would need to do. He said once it's on the rotisserie it'll be easy for him to blast all of the underside. He mentioned using two different media to blast the exterior and the rest of the chassis. At around $1000 per car (maybe less if less media is used) that's not too bad. It's a dustless blasting rig so water is injected with media to reduce heat. He also mixes in a rust protection chemical while blasting then a full rinse down once done. I'll post pics once it gets going here.

Once the blasting is done both cars will get an epoxy coating throughout.

Posted by: Cairo94507 Mar 24 2021, 07:30 AM

I agree re the dry ice blasting, but I think that is the most expensive option available.

Posted by: 930cabman Mar 24 2021, 07:46 AM

I would not dip, there are too many hollow sections with spot welded seams. How can you ever thoroughly rinse these areas and protect from further rust? I have blasted and used paint removers in the past, I would say 50/50 with either method.

Posted by: mate914 Mar 24 2021, 09:36 AM

I used baking soda mixed with aluminum oxide on nicely painted panels.
On the chassis I used coal ashes from tractor supply $10 per 50lbs....works better than sand and with less chems in the air.
Plus all those people charging cars from burning coal to save the planet, by reusing it we are being green!
Matt

Posted by: PanelBilly Mar 24 2021, 01:24 PM

I used some plumbing plugs to seal off the heater tubes. Got them from Home Depot. They are used to seal pipes and come in different diameters. You turn the wing it and they expand to fit the hole. After the walnut blast I cleaned for hours. Blowing air with the compressor while running the value at the same time. I haven’t found any sand since but it might just be sealed in the paint.

Posted by: 914werke Mar 24 2021, 05:01 PM

Both media blasted (dry) and soda blasted (wet) a few cars.
Media is beneficial in that you can mix types Sand for rust & structural areas & plastic or walnut or some other softer less heat generating media for panels & any thin area prone to warping from the heat generated.
Soda was interesting in that it cleaned off paint down to bare metal that exposed the sheet steel manufacture markings !!
Frget about rust, surface or deep corrosion . Wont touch it. So That is still another task.
Never dipped anything. As was commented youd still have to curt open the longs if dipped.

Posted by: racerbvd Mar 24 2021, 05:17 PM

Back when you could reasonably get a tub acid dipped and more places did it, we would spray the tubs with Pam to protect from rust for the trip to the powder coater ( in this case, as with all our powder coating, PowderTech-Plus) who would put the tubs in their big ovens and literally bake the acid and Pam out of the tubs. When it came to sandblasting, it seemed that you could never get all the sand out.
The white is clear coat



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Posted by: GeorgeKopf Mar 24 2021, 06:10 PM

I'm going to acid dip my 1974 chassis.

I found a place near me (NJ) that has lots of experience: Netcong Auto Restorations, LLC
Turns out they use MEChemicals in PA to do the dipping.

Then I'm going to have TranslocGT (PA) fix the chassis and replace the heater tubes.

I know, I know. Convoluted, expensive and time consuming.

I'll update my build thread with how it goes.

George

Posted by: gandalf_025 Mar 25 2021, 12:02 PM

This is what my car looked like when it came back from soda blasting
about 4 years ago..

Posted by: d914 Mar 25 2021, 12:10 PM

I did soda on my car.. worked well.. Just needs a mild acid wash after so paint will stick!!! Its also pretty gentle.

Posted by: 930cabman Mar 25 2021, 12:53 PM

How does she look today? would you soda blast again

Posted by: gandalf_025 Mar 25 2021, 01:09 PM

Car looks more like this now..
It was painted immediately after being stripped.

I would do it again if I ever needed another car stripped..

Posted by: mepstein Mar 25 2021, 03:33 PM

What prep was needed to clean off the soda

Posted by: gandalf_025 Mar 25 2021, 04:02 PM

I wasn’t involved in the blasting process.
The body shop that painted the car sent it out
to get blasted..
I just picked it up about a year after dropping it off..