MediaBlasting

[FallujahMedic]

So, I bought a 40lb pressure blaster from Harbor Freight the other day, picked up some blasting media, tyvek, plastic sheeting and all other supplies I thought I'd need. Anyway it came close to $300. After working most of the day on the engine bay and still not done I decided to look again in the local area for someone to blast my '69FB. At the rate I was going it was going to take forever. Today i found a place that would blast my unibody for $500.00. I checked out the place and it looked like he did decent work, it wasn't a fancy place or anything, but the work did look decent. I think I'm going to buy a rotisserie (autotwirler.com) to ensure the whole car gets done properly.

Following the blasting its going to the bodyshop for some serious sheetmetal surgery. How do I prevent flash rust in-between blasting and welding? I didnt really want it primed with 2 part epoxy if alot of the sheetmetal is going to be cut and welded. Also the blaster doesnt do 2 part epoxy primer, but uses a red primer similar to the old "red lead" they used on ships, just minus the lead.

What do you think?

 

[0to100to0]

i have a similar dilemma

i am building a rotisserie and am going to have the car sandblasted (for around the same price) and have to decide what to do when i am welding in patch panels and the suspension.....and i haven't quite decided...i am looking forward to some responses.
one idea is to have the whole thing coated with epoxy and then grinding away the areas that need to be worked on. however, i don't know if you can do bodywork like bondo and plastic filler over the epoxy. anyone know?

i would not recommend not coating it while you do the work, because that can drag on.

matt

 

[65ShelbyClone]

Those commercial sandblasters are extremely high volume and just blast everything off the metal....and the metal itself if you aren't careful. They usually have a V8 engine running on 4 cylinders with the other four used for a high volume air compressor.

It would probably be better to do the bodywork and then blast everything. That way you don't have to worry about putting filler over paint(which I think will work anyway).

 

[blk 02]

I was wondering the same thing. I noticed while watching either american hot rod or overhaulin they blast first then use a sealer to seal and then do the body work, including patch panels. I'm pretty sure plastic filler is compatible with their sealer they use. Also with the car blasted you can get a better idea of what needs to happen, ie replace a small spot or replace the whole panel. I havent actually done this however, I've spent a lot of time thinking about it and interested what others have to say as well.

Graham

 

[0to100to0]

I was wondering the same thing. I noticed while watching either american hot rod or overhaulin they blast first then use a sealer to seal and then do the body work, including patch panels. I'm pretty sure plastic filler is compatible with their sealer they use. Also with the car blasted you can get a better idea of what needs to happen, ie replace a small spot or replace the whole panel. I havent actually done this however, I've spent a lot of time thinking about it and interested what others have to say as well.

Graham

yeah, that's where i saw it, on american hot rod, i think it was an impala, and they had it blasted and then they coated it (with epoxy?) and did the bodywork on top of that......

matt

 

[shotsy]

Be carefull with the blasting, read this forum, yeah the old crap will come off fast but at what expense. See the link

Sand Blasting body pannel warping heat myth

http://www.hotrodders.com/forum/sandblast-warping-heat-myth-76938.html

 

[FallujahMedic]

Just to clarify, I'm not having the doors fenders, roof or quarter panels blasted, just the main unibody itself. Areas like the engine bay, floorpans, trunk, etc.

 

[milner351]

my friend just had his entire car blasted.

if done right, you can get to bare metal everywhere, without warpage, but, it does take talent on the part of the person holding the blasting nozzle.

The best way to do it is to get it all to bare metal, then clean with compressed air and / or shop vac to remove all the abrasive from the nooks and crannies, wipe down with prepsolvent and tack cloths, then Spray it with self etching epoxy primer. That will seal up everything and prevent any surface rust from starting on the body. As for chassis / engine compartment / etc, I'd use por15, rust bullet, or similar right over the bear metal and call it done.

 

[xoxbxfx]

ok...i have a few cars expirience with this...

First off is finding a good sandblaster (if you choose sand) or a media blaster. Sand is very abrasive and heats the metal to a point it can warp. I would suggest if you are going to do sandblasting trya nd find a reputible shop with someone very expirienced. We have a local guy in dallas and his blaster (mexican dude) has 24 years blasting expirience or soemthign like that. He knows what hes doing and we NEVER worry. They have blasted 2 cars for us, a truck bed for a friend and I have seen numerous 50's cars and a couple machs on rotisseries there. I would definately pay up to $1000 for a quality job with a good blaster than $500 on some dude that does industrial equipment for a living. A unibody usually costs us around $650 inside and out.

Now about body work. With sandblasting and especially media blasting like plastic bead or soda, there is a film left on the car that needs to be washed off before paint BUT it helps keep it from rusting. With sandblasting there isnt that protective layer. I would recommend POR15 inside the car, bottom of the floors, engine bay, and inner fenders. A fresh sandblasted car can sit inside for a couple weeks to months depeding on humidity without really rusting. flashrust isnt going to kill you. Dont rush into primer unless you are going to store it outside. Hell, por15 stick better to rust. I would suggest doing your bodywork before priming the car. Flashrust will come off with some 40grit on a d/a sander without any effort. I have been to bodyshops with cars sitting bare metal outside for a week (couple days in the rain) and no problems. Do your metal work then primer.

If you are paranoid or worried about flashrust, go ahead and epoxy prime it. The areas you cut out and weld in need a good 1" section on both sides of the weld were the paint is sanded off and then do the metal work. Either way, its gonna get primed AFTER the metal work and AFTER the bondo. You can bondo bare metal if you wait on the primer till after the metalwork is done.

 

[68rustang]

I had mine done for $450.00. Best money I have spent on the project thus far. To be safe, blast everything you want blasted, prime and seal it, then do your bodywork. Just spraying primer will not really protect it primer can and will absord moisture over time. To really protect the metal it has to be sealed. Filler can be applied over epoxy primer or the primer can be sanded off first, to each their own. I do not recommend doing the bodywork, and then having it blasted. It is inevitable that during blasting something will be uncovered that needs to be fixed that will involved removing bodywork you already did. I have a few posts outlining my sandblasting experience but they may have been lost in the server crash.

 

[68rustang]

I have been to bodyshops with cars sitting bare metal outside for a week (couple days in the rain) and no problems.

Maybe in Texas but that would not be the case around me or especially in Florida.

 

[havack]

Sand is very abrasive and heats the metal to a point it can warp

Sandblast warping
....the mechanism that creates warpage is not the heat associated with friction of the abrasives hitting the metal. Rather it is the compressive forces induced within the sheet of metal by the heavy abrasive particles hitting the metal surface. You will not see this same warping when light abrasives are used because they lack the kinetic energy required to compress the molecules in the steel sheet thus leaving the sheet in the same stress state as it was in when formed by the dies at the factory.
This is a common misunderstanding, yet this behavior is well understood by some industries and is exploited by those who understand it to improve fatigue life of certain parts (like connecting rods for instance - they are often shot peened to redistribute stresses and place the surface of the rods in compression to reduce fatigue crack propagation)....