Dry Ice Blasting Questions & Answers
Dry ice cleaning is similar to sand blasting, plastic bead blasting, or soda blasting, where a medium is accelerated in a pressurized air stream to impact a surface to be cleaned or prepared. But that's where the similarity ends!
How Dry Ice Works
- What is CO2 (dry ice) blasting?
- It is a process in which particles of solid carbon dioxide (dry ice) are propelled with high velocity air (usually 80-100 psi) to impact and clean a surface.
- How does dry ice blasting remove contaminants?
When removing a brittle contaminant such as paint, the process creates a compression tension wave between the coating and the substrate. This wave has enough energy to literally pop the coating off from the inside out.
When removing a malleable or viscous coating such as oil, grease, or wax, the cleaning action is a flushing process similar to high-pressure water. When the particles hit, they create a high velocity ice flow that flushes the surface.
- How does this differ from how sand blasting works?
- Sand blasting is similar to using an ice pick whereas dry ice blasting is similar to using a spatula. Sand cuts or chisels away the contaminant. Dry ice lifts it away.
- What happens to the dry ice once it strikes the surface?
- It sublimates and returns to the atmosphere as carbon dioxide (CO2) gas. CO2 is a naturally occurring element that constitutes less than 4/100th of 1% of our atmosphere.
- What happens to the contaminant?
- It moves from an undesirable area where it can be dealt with more easily. If it is dry, it usually falls to the floor where it is swept away or vacuumed during normal maintenance. If it is a wet substance like grease, you take a methodical approach similar to hosing down a driveway. You start at one end and guide it to a collection point where it is vacuumed or squeegee up.
- Does dry ice blasting damage the substrate?
- Generally no. There is an energy threshold at which disbanding will occur. When the disbonding threshold is lower than the damage threshold you can clean without damage. If the reverse is true, damage can occur. Most CO2 applications deal with production equipment (cast iron, tool steel, tool grade, aluminum), so there is no damage. We also successfully clean softer substrates such as plastics, wiring, pure copper, and fabrics. Technical support can recommend a machine best suited for delicate applications.
- Can dry ice blasting be used to clean hot online?
- You may be able to clean as much as three to five times faster hot than cold. Most contaminates have weaker adhesive strength when hot. In addition, because dry ice subliminates on impact, there is no media entrapment. Grid entrapment is an important reason those who clean with sand, glass beads, or other abrasive media cannot clean online.
- Does the dry ice cool the substrate?
- Yes, but generally not as much as you might think. The amount of cooling depends upon three main factors: a) mass of the targeted surface; b) dwell time and c) ice usage rate. Typically, a tire mold may drop from 350 degrees F to 325 degrees F during cleaning. With a very thin mold, the drop can be much greater. Generally, however, cooling is not a concern and only rarely does it affect cleaning performance.
- Will the temperature drop damage the substrate?
- It is unlikely, but it depends on the mass of the targeted object. Heavy molds, for instance, will not be harmed in any way because the drop in temperature is insignificant when compared to the mass of the mold. With thin substrates where tolerances are critical, some testing may be required to determine if the drop in temperature would structurally alter the surface.
- Will the process cause condensation?
- Only if you cool the substrate below the dew point which varies depending on local climate. If you’re cleaning a hot mold, you’re unlikely to cool the mold below the dew point, so condensation is rare.
- How did the technology originate?
- It originated at Lockheed in the 70s when a coatings engineer, Calvin Fong, was researching ways to rejuvenate aircraft primer. The technology was introduced commercially in 1987.