the dry ice blasting process, dry ice (CO2) particles are propelled
to supersonic speed impacting and cleaning a surface. The particles
are accelerated by compressed air, just as with other blasting methods.
Overall, there are three steps involved in dry ice blasting. It
can be better understood in the following example.
Click on the DOWN ARROW in the diagram below to see a depiction of the dry ice blasting process:
The Three Step Process of Dry Ice Blasting
#1 - Energy Transfer
With dry ice blasting,
dry ice pellets are propelled out of the blasting gun at supersonic
speed and impact the surface. The energy transfer knocks off the contaminant
without abrasion. The force of this impact is the primary means of
#2 - Micro-Thermal Shock
The cold temperature during dry ice blasting of
the dry ice pellets hitting the contaminant creates a micro-thermal
shock (caused by the dry ice temperature of -79º C) between the
surface contaminant and the substrate. Cracking and delamination
of the contaminant occurs furthering the elimination process.
#3 - Gas Pressure
The final phase
of dry ice blasting has the dry ice pellet explode on impact, and
as the pellet warms it converts to a harmless CO2 gas which expands
rapidly underneath the contaminant surface. This forces off the
contaminant from behind. The contaminant is then relocated, typically
falling to the ground.. Since the dry ice evaporates, only the contaminant
is left for disposal.