What is ultrasonic cleaning?
Ultrasonic cleaning uses high-frequency sound — typically 25–40 kHz — to create and collapse microscopic bubbles in a liquid bath. The collapse, called cavitation, scrubs surfaces the eye cannot reach: blind holes, cross-drillings, thread roots and blind bores. It needs a low-foam chemistry to work.
- Typical frequency
- 25–40 kHz
- Bath temperature
- 55–65 °C
- Concentration
- 1–5%
- Foam requirement
- Low-foam only
The cleaning is mechanical, not chemical. A transducer drives the bath through compression and rarefaction cycles; during rarefaction, dissolved gas and vapour form tiny cavities, and during compression those cavities implode. Each implosion is a microscopic jet that strips soil off the surface it touches.
Frequency sets the trade-off. Lower frequencies around 25 kHz produce larger, more energetic bubbles — better on heavy soils and rugged parts, but capable of eroding soft aluminium or polished surfaces if run too long. Higher frequencies around 40 kHz give gentler, denser cavitation suited to fine components and precision cleanliness work.
Chemistry choice is where most ultrasonic installations go wrong. A foaming cleaner destroys cavitation: foam bubbles cushion the implosion and the bath goes quiet. Ultrasonic work needs a low-foam concentrate, held at 55–65 °C, at 1–5%, with the bath degassed after every fresh make-up.
