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 The same press after cleaning.
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Following illustrations show the cleaning action of CO2. Unlike the grit particles, a CO2 pellet striking the surface does not bounce back. It penetrates the coating, mushrooms under the coating as it strikes the substrate, and then sublimes, as shown in the first Illustration
Cleaning Action of CO2 Pellets Diagram
The thermal shock phase occurs at the upward sloping of the curve, as the CO2 pellet strikes and penetrates the contaminant. The Mushroom effect phase is the time when the CO2 pellet explodes and mushrooms along the substrate, represented by the downward sloping portion of the curve. The maximum mushrooming effect occurs approximately at the end of the curve, as it reaches the horizontal axis, as shown in following illustration.
Click here to see the second diagram
The particle velocity of the grit particle, compared with CO2, has a very high impact pressure, with more potential damage to the substrate. More importantly, removal of the coating occurs only during the deformation phase as the grit particle strikes. There is no further cleaning effect during the restitution phase, as the grit particle bounces back.
The CO2 system is superior to grit blasting because of its flushing action, extended cleaning time, expansion effect, and the fact there is no damage to the substrate. Further, with the CO2 process there is no additional residual waste. In addition to materials such as steel and concrete, CO2 can be used to decontaminate soft materials such as wood, rubber, plastic, and aluminium, without damage.
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