Degassing fresh cleaning solution in ultrasonic cleaning systems is imperative if we want to hit a home run cleaning our parts. Omegasonics explains why in this article.
Every time we replace the cleaning solution in our ultrasonic cleaning systems, or top off the solution lost to evaporation over time, we introduce liquids that contain dissolved gasses.
That’s because cleaning fluids pick up air from the atmosphere every time we ‘agitate’ them. We can’t see the gasses dissolved in the cleaning solutions, but they’re there, just like sugar dissolves in coffee or tea. If we don’t remove these dissolved gasses from our detergents before using our ultrasonic cleaning machine, we will not get the desired cleaning results, and we may in fact damage our parts in the process.
Dissolved gasses in the cleaning solution act like vibration dampeners. When we turn on our ultrasonic cleaners with fresh solution, the vibration from the transducers creates a low-pressure pulse in the solution and the gasses heat up. This in turn causes the gasses to collect and turn into (relatively) large gas bubbles.
Eventually, the bubbles will get large enough to float out of the solution, but in the mean time, they absorb all of the pressure waves created, preventing the beneficial ultrasonic cavitation bubbles that clean our parts. That’s because liquids are incompressible, while gasses are compressible.
Ultrasonic cleaning relies on the incompressibility of the cleaning solution to generate high and low pressure waves that cause the formation of cavitation bubbles that implode and remove contaminants. When we don’t remove the gasses prior to use, the large gas bubbles absorb all of the energy, leaving no energy to create cavitation bubbles.
To illustrate the point, imagine that we’re hitting a baseball. The ball leaving the bat is the pressure wave we create when the piezo-electric transducers “strike” the cleaning solution, and the bat is the transducer itself. We want to hit a home run, so we want to hit the ball as far as we can. If we hit a baseball with an aluminum bat, the ball will go a long distance with a lot of force.
Home run! However, if we wrap that same ball in Styrofoam, it won’t go nearly as far or with nearly the same velocity. That’s because Styrofoam is compressible and absorbs the energy from the impact instead of transmitting it to the ball.
In some cases, failing to degas our solution before using it can actually damage parts we place into our ultrasonic cleaners. The dissolved gasses that end up in our cleaning solutions are components of air, and one of those components is oxygen. If we don’t remove as much oxygen as possible from the solution before using it, this can lead to an oxide reaction that may tarnish or rust the parts being cleaned—and in some cases the parts may become brittle.
This usually occurs on parts that oxidize easily to begin with, like cast iron, carbon steel, aluminum, and silver, but it can also affect some types of plastics. This type of phenomenon isn’t normal; the gasses usually boil out before they can severely affect a part’s finish; however, if the level of dissolved gas is high enough, oxidation can occur.
Degassing the solution in our ultrasonic cleaning systems before using them is simple process that must be done. All it takes to degas the solution is to run a 10- to 15-minute cleaning cycle, preferably with heat (if available), without any parts in the solution. The gasses accumulate and boil off, leaving a pure, gas-free cleaning solution available to do what it does best—remove contamination from the parts we place in it.
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