How does ultrasonic cleaning work?

Cavitation step by step

What is
cavitation?

Cavitation is a physical phenomenon in which microscopic bubbles form, grow and subsequently collapse in a liquid due to rapid pressure changes.

An ultrasonic wave creates alternating phases in the liquid:

Negative-pressure phase – the liquid is subjected to tensile stress, causing tiny cavitation nuclei to form.
Bubble growth – during subsequent pressure cycles, the bubbles absorb energy and expand.
Bubble collapse – once the bubbles become unstable, they collapse very rapidly.
Cleaning effect – local pressure pulses and microstreaming occur near the surface, releasing contaminants.

A single cavitation bubble is microscopic. However, an enormous number of them form in the active cleaning bath, and their repeated action creates a uniform cleaning effect.

What is
ultrasonic cleaning?

Ultrasonic cleaning is a process in which parts are immersed in a liquid and cleaned by ultrasonic waves. These waves are generated by transducers mounted on the bottom or walls of the cleaning tank. The transducers convert electrical energy into mechanical vibrations that travel through the cleaning bath.

The result is determined by a combination of:

ultrasonic frequency and power,
correctly selected cleaning chemistry,
bath temperature,
cleaning time,
positioning and orientation of the part,
rinsing, drying and, where required, passivation,
cleanliness and regular maintenance of the bath.

A properly designed process therefore does not begin by selecting the “most powerful ultrasound”, but by assessing the material, type of contamination and required result.

Ultrasound and cleaning chemistry must work together

A common mistake is expecting ultrasound to remove every type of contamination using only water. In reality, ultrasound and cleaning chemistry perform different but closely interconnected tasks.

Cleaning chemistry dissolves, emulsifies or chemically breaks down specific contaminants. At the same time, it must be safe for the material being cleaned.
Ultrasonic cavitation improves contact between the liquid and the surface, helps release the loosened layer and carries contaminants away from complex areas.

Different products are required for oils and grease than for carbon deposits, rust, limescale, abrasive compounds or coatings. Aluminium, steel, stainless steel, brass, glass, plastics and electronic components also require different formulations.

Our experience at Bio HI-TECH confirms one simple rule: equipment power alone cannot compensate for incorrectly selected chemistry. The best results come from the right combination of technology, chemistry and operating parameters.