Well, for starters, it’s a type of cleaning. The “blasting” part of the name evokes an explosion. And that’s sort of correct (at least on a minuscule level).
As you can tell by the name, it uses dry ice, or frozen CO2 if you prefer to call it that.
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| Dry ice pellets being added to dry ice blasting machine. |
Dry ice blasting uses compressed air to accelerate frozen carbon dioxide (CO2) “dry ice” pellets, at -109 degrees F., to a very high velocity. It works somewhat like sandblasting except that the pellets are relatively soft as compared to sand. Also, the pellet changes from a solid to a gas instantly upon impact with the surface to be cleaned, so the process is considered non-abrasive.
Now here is where you have to use a little thinking. The instantaneous change from a solid to a gas upon the pellet’s impact with the surface coating, absorbs heat from the very thin top layer of the surface coating or contaminant. This very rapid transfer of heat into the pellet from the coating layer, creates an extremely large temperature difference and thermal stress between successive micro-layers within the coating. The micro-layers of coating crack under this stress.
If you’ve ever listened to ice cubes cracking when you put them in a glass of hot tea, and you figured out what happened, then you get the idea. That’s thermal stress.
When you combine the effect of the impact energy of the high speed pellet and the thermal stress caused by the extremely rapid change in temperature between the micro-layers of coating, then something has to give way.
But that’s not all!
Remember the “explosion” that the blasting part of the name evoked? When the solid CO2 pellet instantly changed to a gas, it expanded nearly 800 times the volume of the pellet in a few milliseconds in what is effectively a “micro-explosion”. This “micro-explosion” lifts the contaminant particles away from the surface being cleaned.
And that is Dry Ice Blasting.
Blackwell’s Inc.
Industrial Specialty Cleaning
Concrete Coatings and Concrete Repair
LaGrange, GA
706-883-6239
www.blackwells-inc.com
