Sandblast or Media-blast body panels?

[Skydog]

Hello:

I'm wanting to prepare the removed various body panels
for upcoming priming & painting, that I can begin the
process at bare metal.

The barren tub is already beyond this point, as I had
arduously sanded it down by hand &/or machine, and
it has now been initially primed with Eastwood's Rust
Encapsulator. Atop this will be a sprayed-on 2K epoxy
primer, also by Eastwood (which I've already on-hand).

I fret doing the same hand-sanding to each & every body
part, but if determined as a best route, will gladly do so.

Earlier, a sand-blasting company had prepared the chassis.
They did a good job, but I'm concerned that the impact
of the same sandblasting process may be too much for
the body metal - destroying its smoothness.

Am I right about this?

I have not yet looked into other such blasting companies,
who conversely do media-blasting, although I live in the
North Georgia area (Atlanta area and above) - and I'm
sure there's no doubt plenty such companies here.

QUESTION: to properly prepare the various other body
components, is it media-blasting that I must consider?

Or should I go ahead and simply hand & machine sand
the various components, via a labor process, as done to
the tub?

Thanks,
Skydog.

 

[reddingcruiser]

Hey Skydog,
I've prepped all of my FJ40's with sandblasting (except for my current multi-colored work in progress). The trick is finding someone with a good reputation blasting automotive sheet metal and who can select an appropriate sand size (mesh) to give you the best surface possible. Done well it makes everything afterwards much easier. Done wrong it can create a mountain of problems, including unusable parts due to warped metal. Any media that has a tendency to retain moisture (i.e. Soda) is generally not recommended on parts where it can be trapped in joints, seams or laminations, for obvious reasons.
Having said all of that, your first coat of primer should be enough to fill any roughness resulting from a properly done sandblasting job.

 

[TheHardWay]

Years ago I sandblasted (sandbox sand) the hood, trunk lid and doors of a '76 Bimmer in my backyard with an Eastwood gun and a 20 gallon compressor. Didn't warp anything and took everything down to the metal. Don't see why a professional sandblaster couldn't do the same

 

[reddingcruiser]

Years ago I sandblasted (sandbox sand) the hood, trunk lid and doors of a '76 Bimmer in my backyard with an Eastwood gun and a 20 gallon compressor. Didn't warp anything and took everything down to the metal. Don't see why a professional sandblaster couldn't do the same

You would think so, but it's not always the case. Best to ask what their level of experience is with sheet metal. Or, ask local body shops who they use - it's cheap insurance.

 

[TheHardWay]

Good point. That's why I did my own finishing body work and then shot the whole car myself. Never done that before, but it came out great and I saved a ton of dough. Having said that, I never try to convince anyone to DIY if they don't want to.

 

[Skydog]

Dick Thompson & LasCrucer,

I'm Sooo glad I came here and asked... I appreciate your words & advice VERY MUCH !!

From you, I now understand that I should re-approach the sandblasting company (who had very nicely sandblasted the chassis of my FJ40) & inquire if they have specific & successful experience with automotive body parts (perhaps relying upon the trust of their words... though perhaps they'll have past project pictures?). And if not, I will search for an Atlanta area sandblasting company who actually does have such regular experience. I will then search for such a second sandblasting company via recommendations made by local-to-me auto-body repair or renovation facilities.

And from your words here, I'm now understanding that sandblasting (and NOT soda-blasting), if done properly to the sheet metal with the proper grain of sand, will serve as a good starting point for my upcoming paint work on my own FJ40, of which I'm very much wanting to carry-onward as fully DIY (leaving only that of the sandblasting to others).

Thanks again !!!
Marc

 

[TheHardWay]

High five, Dick!

 

[tubalubb]

Up until recently, we had a place here that would dip the entire vehicle in a base solution, guaranteeing dead rust in and out. Unfortunately they have decided to stop that portion of their business. I've been researching alternatives and the most promising i've seen is this dustless blasting rig made in Houston www.dustlessblasting.com (no affiliation) i've really liked what i've seen, no warping, very localized mess etc., there's a good video on eastwood garage. Anyway, I say all of this because they are old enough and experienced enough to have a good distribution system and there are many of their customers out there already who will come to your house and blast whatever without a big mess and you don't have to haul your parts. You can check with them and they may know someone local. I'm seriously considering getting one of these for side work myself. Just a thought.

 

[Vae Victus]

I'd like to add that someone who knows how to media blast auto body panels will know not to turn the pressure up too high. The difference between a small sandblasting unit like we might have at home, like the one I've been using a small pressure pot, and a professional version is the size of the nozzle and the amount of pressure that they can output.

With my small pressure pot I can output about 100 to hundred and 20 PSI in short bursts. But a professional sandblaster can put out 200 psi from a three-quarter inch nozzle very easily and can sandblast a battleship.

If they use that much pressure on a thin body panel it would warp from the heat at best and possibly burn completely through it where there was a bit of rust at worst. Some might argue those are in reverse order.

Rainman who has a build thread on here on the truck called 2NDCHNC, had this exact experience happen to him on his door panels. They were warped by the painter who didn't know what he was doing although he is very experienced, and they had to use a lot of filler and a lot of sanding to get them smooth again. The downside is that they now have a whole lot of filler on his doors which had no reason to have filler in them beforehand.

Another thing to note is that sand is not really used much anymore, especially by professional sandblasters. They all use some kind of media that is not sand based because of silicosis a lung disease that can be created through inhalation of the sand particles.

Most people now use things like aluminum oxide or coal slag or various grades of other natural hard media, or softer things like soda as was Artie mentioned, walnut and/or corn cob and other soft media like that.

Acid dipping is a great way to completely remove everything down to the bare metal, where as sandblasting can still trap rust particles in the layers of metal. The amount that this is done is far less than what is done when we use a wire wheel to scrape the rust and paint off of metal. Sandblasting is considered one of the best and most readily available ways to prep metal for painting.