Scale deposit removal by means of ultrasonic cavitation

This paper presents a study of the mechanism of acoustic cavitation-generated erosion on metallic specimens coated with calcium carbonate (scale). Specimens were produced by scale deposition on steel substrates with different surface roughness, and then exposed to sonotrode-generated acoustic cavitation. The rate of scale removal was determined to be proportional to the pressure amplitude generated by the sonotrode. Descaling can also be intensified by reducing the substrate surface roughness. However, the scale destruction mechanism is largely dependent on the microstructure of the scale deposit, as local inhomogenities may intensify the erosion rate. Scale deposits can, depending on the hardness of its surface and substrate surface finish, either be eroded layer by layer, or by breakage of larger areas. Regardless of the exact descaling mechanism, the edge length-to-area ratio of descaled surfaces decreases with time, leading to a gradual reduction of descaling efficiency. [Display omitted] •Ultrasonic cavitation scale removal from metallic surfaces was studied experimentally.•Calcium carbonate deposits are in form of porous aragonite structure.•Descaling is more efficient at higher amplitudes of pressure pulsations.•Descaling efficiency decreases with the surface roughness of metal.•Specimens with less homogeneous initial scale layer are descaled more rapidly.