Media Blasting



sandblasted alternator coverMedia blasting also known as Sandblasting is a great preparation method for Powder Coat. . When powder coating, it is very important for the item you are coating to be completely clean of oils, dirt, paint, rust, corrosion, and damaged plating (zinc, nickel, chrome, etc). All of these things can interfere with the powder coating process causing imperfections in the finish or causing it to fail completely. After cleaning your item of all oils and dirt, a Media Blaster does this job very well and very easy compared to other methods.






You can see the before and after of sandblasting below.



sandblasting brake master cylinder powder coating


Another advantage of using a sandblaster to prep your items for powder coating is it gives the item a surface profile or "tooth". Think of sanding a piece of metal with sandpaper and you see the thousands of little scratches that it leaves. These scratches create high points and low points in the metal. This is called a profile. A profile allows the powder coat to seep into all of these high and low points which allow it adhere to the part much better than if the metal was completely smooth. While sandpaper does give your item profile, the sanding marks are in straight lines, a sandblaster creates a uniform textured finish all over the entire surface of your part, and in places that no sandpaper can reach. Without a surface profile, powder coating can just peel off the surface, this is called delamination.


Pretend this picture is a microscopic view of a powder coated surface and decide which surface would allow the coating to adhere better.

powder coating sandblasting media blasting profile tooth adhesion


A sandblaster is usually gun shaped and it uses high pressure air to propel sand or other media. When this media hits the metal, it can knock off rust, scale, dirt, paint, or other coatings giving you a clean bare metal surface. This sandblasting gun can be placed inside of a sealed cabinet to contain all your media and allow you to reuse it. This cabinet is  called a blast cabinet. There are also free standing sandblasting guns that can be used anywhere, but with these, you must wear some protective gear.


To use a sandblaster, you will need an air compressor to supply you with this high pressure air, and a sandblaster consumes a lot of air so you will need a decent sized compressor. To see what kind of compressor you need or to see if your compressor is up to the task, take a look at "Choosing an Air Compressor"  Many sandblasters out there state that you need at least an 2 stage 80 gallon air compressor that puts out at least 15cfm@90psi to sandblast. Air compressors are not cheap, even used, so while a huge compressor like that would be ideal, you CAN make due with a smaller compressor. The general rule is to buy the most compressor you can afford, but if you can only afford a 5 gallon pancake air compressor, keep saving! I personally use a Husky 60 gallon air compressor that puts out 11cfm @90psi which is enough to blast continuously, however the I do stop to give the compressor breaks.

Sandblasting also requires very dry air from the air compressor.  Otherwise the media mixes with the moisture and causes frequent clogging.  Another downside to this is, is that when powder coating, you want your part to be perfectly clean after sandblasting.  If you are blasting with oily, moisture laden air, then this will likely cause defects in the finish.  See How to Dry Compressed Air for more info on this.




Siphon Feed or Pressure Pot Sand Blaster?


As far as sandblasters go, there are 2 main types: "Siphon Feed" and "Pressure Pot". A siphon feed sandblaster generally looks like a gun, it can have a trigger or a foot control pedal. The gun has 2 connections. One is an air supply line from your air compressor and the other is a media pick-up hose which is a larger diameter hose that you can stick in a bucket of media. As the air passes through the sandblast gun, it uses a venturi effect to suck the media through the media hose and force it out of the nozzle of the gun. This style of sandblasting gun is cheap and gets the job done.  Another great thing about these sandblasting guns, is you can stick the pick-up tube in baking soda and use it soda blast.  It is not quite as efficient as a dedicated soda blaster, but I have used it to soda blast 100 pounds of nuts and bolts with no problems.

This Skat Blast Sandblasting Gun is the gun in my cabinet.  This is the best sandblasting gun I have used and it is worth the price. The long handle makes it very comfortable to use since it requires very little effort to keep it depressed. It also feels more powerful than cheaper sandblasting guns and makes quicker work of sandblasting jobs.  It comes with a steel nozzle, but after it gets worn out, I recommend using ceramic nozzles as they last much longer, or even better would be a carbide nozzle as it will last a very long time.




There are different versions of the gun and nozzles available for different air compressors:

Air Compressor Output      Gun                            Nozzle
4-9 CFM                                 S-35 Small                 Small Ceramic
10-15 CFM                             S-35 Medium             Medium Ceramic / Medium Carbide
20-25 CFM                             C-35-S Large              Large Ceramic   
25+ CFM                                High-Volume Gun      High-Volume Head




I also have a Campbell Hausfeld gun as a backup gun.  It is cheaper but it seems to make the entire sandblasting process take longer.  With all things being equal, the Skat Blast gun just finishes jobs quicker than the Campbell Hausfeld gun. The trigger is also much shorter on the Campbell Hausfeld gun so it requires more effort to depress it. After sandblasting for awhile, it is noticeably less comfortable than the Skat Blast gun.  That being said, it is still a good gun for the price. It comes with its own media tube so you can use it inside of a blast cabinet or you an stick the tube in a bucket of media and use it anywhere. It also comes with a ceramic tip which lasts much longer than steel tips.   However, if you plan on sandblasting on regular intervals, I highly recommend the the Skat Blast gun instead.  









A pressure pot blaster generally looks like a propane tank with legs. It has a lid on top to pour media into and a smaller valve on the bottom where the media exits and goes to your sandblasting nozzle. The air supply from your compressor actually goes to the tank and to the valve at the bottom. This way the media is pressurized.  This way the media is being forced out of that valve at the bottom and then the other air line is forcing that media + air to your sandblast nozzle.

pressure pot sandblasterA pressure pot blaster is more efficient than a siphon blaster. It uses less air and blasts about 4 times faster than a siphon-fed blaster. If you have a big job to do with a lot of surface area, a pressure pot is the way to go. However, they are more of an "outside" or in a "blasting room" tool. Once the tank runs out of media, you will have to either add new media, or sweep up the media on the ground and pour it back into the tank. If you recycle your media like this, make sure you filter the media somehow. I have a piece of widow screen that I folded over itself to make it filter more finely. A small rock can clog the machine. 







Sandblasting Cabinet:

Now that you understand the types of blasters, there are several environments where you can do your blasting. Blasting is a messy process. It creates lots of dust that will coat an entire garage, it throws media everywhere, and the media that hits tends to sting a little. Blasting can also be dangerous, a powerful blaster can take off skin. Media bouncing back at you can cause damage to your eyes, and the dust can damage your lungs, especially if using sand as your blasting media. So keeping that in mind, you can blast outdoors with some personal protection equipment, you can dedicate an entire room to blasting which will also require protective gear, or you can use a sand blasting cabinet.




powder coating sandblasting cabinet with light and media reclaimer vacuum
With a sand blasting cabinet, the blasting process takes place inside a completely enclosed box. There is a window for you to see what your doing and long heavy duty gloves that are sealed to the front of the cabinet. The cabinet has a grate that you will place your items to be blasted on, and below that is an area for the blasting media to fall down into. Blasting cabinets are usually paired with siphon feed guns. The media falls through the grate to the bottom of the rack as your blasting, the media pick up tube is positioned down in the base of the media and the other end connects to your gun. This way you can blast endlessly and your media is constantly recycled. You will need good lighting to see what you are doing and also some type of dust collector. As you are blasting, the media will brake down into finer and finer dust which constantly floats around making it very hard to see. The dust collector will suck this fine dust out of the cabinet which increases visibility. There are purpose built dust collectors and there are some DIY methods such as hooking up a shop vac to the cabinet.  The easiest method is to buy a quality sandblasting cabinet that comes with a dust collector and lighting.  The sandblasting cabinet pictured comes with everything you need to start blasting and it roomy enough to do wheels and other large parts.  There are cheaper sandblasting cabinets available if you do a little DIY work.  The cheaper cabinets usually need sealed up with caulk and some kind of DIY dust collector will need to be implemented.  Read how to setup some DIY dust collectors in "Media Blasting Part II"  If you have the room in your garage, I recommend a stand alone blast cabinet over the bench top blast cabinet.




Here is a bench top sandblasting cabinet. They are smaller, and don't have the funnel on the bottom that lends to easy media changes. However they can sit on a bench in the garage, taking up less room.  
bench top sand blasting cabinet






What Media to Use?


There are many type of medias to choose from when blasting. Having the ability to blast opens up a lot of options in the garage, not just for powder coating. For now, I will talk about the type of media that you want to use for powder coating prep.

powder coating sand blasting media black diamondCoal slag: This media is very cheap, it leaves a good profile, and it lasts a pretty long time. It is great at stripping paint and rust very fast. Examples of coal slag is the popular brand: Black Diamond, its sold at Tractor Supply Company. 50lbs is about $7.



Aluminum Oxide: This is a very aggressive media that easily removes rust, paint, and is more efficient at removing powder coat than the coal slag. It is pricier, but it lasts longer. This leaves a great profile in a steel or iron part to be powder coated. If you are doing any ceramic coating, you must use aluminum oxide to prep.  Although when blasting aluminum, you need to be careful not to leave too much of a profile, as aluminum is much softer than steel. Hold the gun back further and lower the air pressure.

Sand: Sand is the cheapest. You can get a bag of play sand from Home Depot for next to nothing. However, sand is very dusty, making it almost impossible to see in the cabinet. Sand also produces silica dust when blasting which can severely damage your lungs even when using a cabinet.  The only safe way to use sand is with a supplied air breathing system.

To continue reading about media blasting, click here: Media Blasting Part II

20 comments:

  1. Thank you for posting this! I found it very helpful. I have been trying to find powder coating services in Illinois, but dont know what to really look for. Do you have any suggestions as to what to expect and look for in a powder coating service?

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  2. This appear to be great equipment that facilitates effective powder coating. Thanks for sharing

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  3. To be clear, If I use the grounding rod, I no longer need the alligator clip on the eastwood?

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    1. Yes that is correct. Once your parts are connected to the ground rod, you no longer need the ground clip that come with the eastwood guns.

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  4. Hey Sean- SidVicious again. I picked up my compressor & blast cabinet today. Besides Alum Oxide, what would you recommend for stripping aluminum? I've heard walnut shells are good- but wanted to get a second opinion.

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    1. I personally use Black Diamond Coal Slag blast media from Tractor Supply Company. I use the one marked "fine". It comes in 50lb bags for around $7 which is a great deal. However, it is pretty aggressive when you first take it out of the bag, so I like to wear it down a little bit on steel or iron parts before I use it on aluminum. Aluminum oxide can be even more aggressive than the Coal Slag, but powder coating shops will still use both on Aluminum. It is good to use a reduced psi, try 60-70psi and keep a little distance from the part with the blasting gun. Walnut shells are probably too soft, they are great for removing paint on delicate parts, but they will not leave the desired profile for powder coating. They also leave oils on the parts which would not be good for a powder coating. Of course, you can degrease it again, but I see no reason to add possible problems.

      So just to re-cap, Coal Slag or Aluminum Oxide would both work fine on Aluminum, just don't blast at point-blank range and lower the blasting pressure down to around 60-70psi with your regulator.

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    2. Awesome. Thanks very much. I start putting everything together tomorrow.

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  5. I use sand in a small portable blast hopper from Sears in the backyard. The sand goes on the ground no clean up and little dust to worry about. I am careful about the toxicity of material I removed from parts cleaned.

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    1. Even though the sand all eventually lands on the ground and leaves no cleanup, the dangerous part about the sand is the microscopic particles that are flying around while you are blasting. You do not want to breath blasting dust, especially sand. I recommend either switching to a safer blasting alternative like aluminum oxide or coal slag, or wearing a supplied air respirator if you want to stick with sand.

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  6. hi any one know how to remove acralyic paint from matel iam from pakistna here no any things like soda blasting can any one help me how to make soda blasting my self
    my contact no add
    faraz.scn@gmail.com
    00923152328918

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  7. Do I need to go through the same blasting process you mentioned above for bare aluminum? Also, can you use soda for prepping aluminum?

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    1. Yes, aluminum should also be media blasted to provide a profile. Soda blasting, while great at cleaning up parts and removing paint does not create any profile or tooth on the parts so it is a poor choice for blasting with. I personally use soda blasting to clean up gasket areas and stuff like that because it is so delicate.

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  8. so after the sand blasting is there any more further cleaning that needs to be done like a finale wipe down with something ??thanks

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    1. My post-blast cleaning consists of blowing off the part with air while brushing it with a clean stiff-bristled brush to remove any stuck media. I only handle the part with clean gloves after it comes out of the blasting cabinet. I find that this is the only level of cleaning necessary after blasting. However, if you do touch the part after blasting or accidentally drop it on the floor, it can be cleaned off with denatured alcohol and a low-lint towel. This often leaves lint and fuzz on the part though. Many powder coaters then use a torch to go over the part and burn off the fuzz.

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  9. I have billet aluminum door handles with chipped chrome plate. Should I blast the plate off before powder coating?

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    1. Yes anytime the chrome is compromised, it must be completely removed before powder coating. IF you are to blast it off, then you can go that route. However, most chromes, when adhered well are a pain to blast off and have to be taken to a chrome plater to have them remove it.

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  10. Sand blasting can make the part a new because it remove the all paint or rust from the part.

    Silica Sand Exporter

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  11. I have a custom sport bike i'm building and need advice on the best media for for cabinet blasting aluminum parts. 99% is aluminum and want to make sure i'm getting the right profile for the job without worries of impregnation?

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  12. Is 80 grit steel blast media a good type of media to use

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  13. This is a great resource! I have some aluminum enclosures that need to be sandblasted prior to powder coating. I need a media that can remove tooling marks from the CNC mill, yet is fine enough not to destroy the features on my part. I've been recommended 120-grit aluminum oxide for this, but thought I'd ask for opinions here. What do you recommend?

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