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Media Blasting and Surface Prep


ChrisRice

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I just got a new 60 gallon Kobalt compressor and 3/4 iron lines run through my shop and I am ready to put them to good use.  I purchased a 20 gallon media blaster.

 

This being said, I used to work as an industrial media blaster (using black beauty coal slag primarily) so I am familiar with blasting.  I am trying to figure out how much blast media I will need to blast my 1955 Plymouth suburban (inside and out) including frame.  When I used to do this, if i ran out, my employer just got more.  But not having a place to store tons of it, I dont want to over or under order too much of it and have lots of wasted material. I dont have an easy way to "catch" the material for reuse.  Any estimates on how much I might need?  Also, on the outside, there is not much paint left, and the body is mostly rust.  Any suggestions on type (fine/ coarse/etc.)

 

Also after blasting, suggestions on cleaning/etching the metal and type of primer to use?  Also is a sealer necessary as I wont be going strait from primer to finish immediately.  If so, suggestions on type?

 

I know some of you will argue against blasting, urging me instead to wire wheel, but on this big of a body, that is just not feasible.

 

The finish coat will be of a factory type, color Biscayne Blue Metallic.

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Do NOT blast this. Do NOT wire-wheel it. Even if you don't live to regret it, the next caretaker certainly will.

 

It sounds like it doesn't have an old re-spray on it now, which is good.

 

The best process will be to sand the old finish using good air tools or by hand. Using high quality wet sandpaper this will go amazingly fast.

Once you get to an even old finish, or bare metal, use a good epoxy primer.

 

Blasting body panels warps metal, removes too much metal indiscriminately, and creates a surface that requires too much primer and filler, which can never be properly restored.

 

Confine any blasting to frame and other really thick parts such as the engine block.

 

Don't become a DPO!

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Do NOT blast this. Do NOT wire-wheel it. Even if you don't live to regret it, the next caretaker certainly will.

 

It sounds like it doesn't have an old re-spray on it now, which is good.

 

The best process will be to sand the old finish using good air tools or by hand. Using high quality wet sandpaper this will go amazingly fast.

Once you get to an even old finish, or bare metal, use a good epoxy primer.

 

Blasting body panels warps metal, removes too much metal indiscriminately, and creates a surface that requires too much primer and filler, which can never be properly restored.

 

Confine any blasting to frame and other really thick parts such as the engine block.

 

Don't become a DPO!

 

Woah, that is the first time I have ever heard someone say don't sandblast to remove rust.  What examples do you have that show warping or metal removal?  I just was sandblasting my wheel fenders and saw no issues when I was doing it.

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From my understanding you have to keep the heat down to prevent warping.  

 

This is what is looked like two years ago.. As you can see, sanding by hand isnt going to happen at a rate of speed that will allow me to finish before starting over again.

post-6402-0-61073100-1427477359_thumb.jpg

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Do NOT blast this. Do NOT wire-wheel it. Even if you don't live to regret it, the next caretaker certainly will.

 

It sounds like it doesn't have an old re-spray on it now, which is good.

 

The best process will be to sand the old finish using good air tools or by hand. Using high quality wet sandpaper this will go amazingly fast.

Once you get to an even old finish, or bare metal, use a good epoxy primer.

 

Blasting body panels warps metal, removes too much metal indiscriminately, and creates a surface that requires too much primer and filler, which can never be properly restored.

 

Confine any blasting to frame and other really thick parts such as the engine block.

 

Don't become a DPO!

 

What is a DPO??  It does have what is left of a poorly done old re-spray by a less than amateur "restorer." 

Edited by ChrisRice
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I must aslo strongly disagree with the above statement..I have sandblasted whole cars..the secret is not farming it out but doing it yourself...properly regulated sand flow and pressure will do the job easily and NOT warp or remove any excess amount of metal  that is usually confined to commercial blasters where time is money and wide open flow and air pressure cuts time to a minimum..

 

learn what not to do with your pressure pot...#1 no no in my book is using the deadman to control sand..use it only to guide the air..again this is not commercial operation..you call..you plugged lines and loss of sand between start and stop

 

as a side note to another part of the original question..I used less than 20.00 in shand and stillhad 50% left over when the job was done..back drop, recycle and you can get a lot of mileage from your media...I used standard .030 grit from the commercial sandblast supplier...

Edited by Plymouthy Adams
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wide open sand is never good, even in the industrial applications i used to do.  low sand, decent pressure.  I imagine both would be lower on this thin of metal.  Plymouthy, any suggestions on pressure, etc.?

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you need to answer if you have control of the air to tank and deadman line individually controlled...another key in set up....not sure of your pressure pot, who made it and how it is set up..you also will want a water sepeator at the inlet to the unit also...last thing you need here is moist sand..moist sand will compact in you tank in a nanosecond...rigging a regulator here will be a plus...

 

if you have ever used a paint pot..think similar for the sand pot..

Edited by Plymouthy Adams
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There are a number of places that use materials other than sand to clean cars and remove all rust that do not distort the metal. These same places also do aluminum without any problems. Why not check with such businesses to find out what they use? As to quantity of material they should also be able to answer that question if you are using some kind of recovery setup. Epoxy primer would be the best for you since it primes and seals.

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other media will leave a residue...I would strongly suggest that you do research what is what and how it is used and the clean up of the mess and the substrate after the fact....another place where urban legend and hearsay can get you in trouble..and get you there quickly...really not much out there that does not have an advantage and also disadvantage over something else..you best weight that for yourself and what you are willing to follow up with after the fact...

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I do have individual air/sand controls on my blaster, as well as having a regulator and a water separator at the inlet so that part is covered.  Plymouthy, you said that you used less than 20 in sand at a .030 grit sand.  Was that 20 pounds, i assume? I will not be able to capture and reuse, so i know that i will need more then that.  i had thought i wouldve needed somewhere in the 100-200 pound range.

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I have a 1951 Dodge B-3-B that I am in the process or restoring to original condition. The sheet metal is solid except for some holes on the floor in front of the passenger seat. The truck was repainted at some time in the past and I intend to strip off the old paint using a newer process called DUSTLESS BLASTING. Because it uses water, a small amount of rust inhibitor, and a crushed bottle glass media it isn't supposed to warp sheet metal (the water keeps it cool). Has anyone tried this method of paint removal? It looks like a pretty good system to me because it isn't supposed to be as rough as sand blasting and it doesn't make a mess like soda blasting. Here's a link to the Dustless Blasing web site: http://www.dustlessblasting.com/. Has anyone on the p15 d24 forum tried this? If so, what kind of results did you obtain?

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so you telling me you can set your pot at x pressure and also at the same time set your line for a different x pressure?  this is typically not  your stock out of the box set up...while the ball valve will control the sand flow and the inlet to the hose and another for the tank individually...you need a regulator for the individual pressure..

 

20.00 is not in pounds but in dollar amount...of course that would be a tad more now as inflation eats everything...

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I'm hearing reports now of soda blasting, (baking soda).  Anyone tried that yet?  Here's one source.

 

http://www.northcarolinasodablasting.com/

 

reports are one thing..first hand another...clean up yet another and again the actual residue...lthis stuff is nasty..usually reserved for light aluminum and fiberglass blasting...suggest you read a bit more..lots of folks do not use this media in the proper manner...

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so you telling me you can set your pot at x pressure and also at the same time set your line for a different x pressure?  this is typically not  your stock out of the box set up...while the ball valve will control the sand flow and the inlet to the hose and another for the tank individually...you need a regulator for the individual pressure..

 

20.00 is not in pounds but in dollar amount...of course that would be a tad more now as inflation eats everything...

Perhaps, I explained it wrong.  There is a ball valve at the bottom of 'tank' to control sand flow, another at the air flow, a third at the deadman, and a fourth at the inlet to shut off.  I can individually control the amount of air and sand mix through the two appropriate valves.  Yes i know, the ball valve for the sand will get 'eaten up' over long term like this.

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reports are one thing..first hand another...clean up yet another and again the actual residue...lthis stuff is nasty..usually reserved for light aluminum and fiberglass blasting...suggest you read a bit more..lots of folks do not use this media in the proper manner...

Soda blasting will remove paint, but not rust.  But then there is the issue of cleaning the metal afterwards, as the soda will turn into a fine powder and embed itself deep into the metal.  As Plymouthy said, it is best used only for aluminum and fiberglass, as it will not eat up the fiberglass.

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Chris..you need pressure control along with flow control...yes  as stock they have a number of ball valves...you still need the ball valves..just add one more reg for tank ad you split the incoming ahead of the main air ball valve..then just control the line from the main line regulator most folk already have on their tanks..if you do not have a line regulator there...you will need another regulator..flow control allows you to kill the air pressure as you service the tank...without having to disconnect the lines...

 

the nozzle valve I would suggest leaving open and control all sand flow from ball at the combination port at the bottom of tank..even with a bit less pressure on the tank than the air nozzle..you will get yet a heavy flow...this is what you do not want...as an added note here...increasing the leg height on the pot makes this ability to control all the much easier...again..most things are produce at a minimum cost...to tweak for prime use often requires a bit of user intervention..

 

sand flow at the nozzle control only leads to a clogged line and much spitting and sputtering and loss of sand that is a bit pain filling as it is...

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I use one of those small hand blasters that are about fifty bucks on my garnish mouldings.  It's not a harsh blast and takes everything down very nicely.  I can't imagine trying to sand out rust and rust pits by hand.  After blasting, I hand sand with 150 grit and finally with one of those 3M yellow pads, fine (180)  Comes out smooth as a baby's you know what.

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yes Bingster..big big difference in someone doing it at home with controlled process verse some commercial enterprises...as with all things...it is a process that is often learned but with right approach is not expensive nor is it destructive and the results..well it is what you make it..

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I'm almost at the point of having the coupe soda blasted.  I haven't seen much bad press on it.  What's the cons for soda?

 

It depends on why you're blasting it.  Are you trying to save chrome, non steel pieces, and don't have any rust?  If so, then it's perfect, but if you are trying to get rid of rust, it's not going to help out.  Also you're supposed to use a neutralizer after you soda blast or they say it can leave a film that discourages paint adhesion.

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Just to remove paint mostly.  I've read that the body will need to be washed well afterwards.

Go for it then, but just know you'll have to get or rent a pretty beefy setup to do it.  It'll save you a lot of time, and energy for sure.

Edited by 1940_dodge
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