High intensity ultrasound causes the formation of cavitation bubbles which collapse in a manner that, in the presence of a solid surface, form high velocity fluid microjets directed toward the surface. The intense fluid agitation at surfaces in a focused ultrasound field enhances transport of momentum, heat, and mass and influences the behavior and integrity of surface films on metal electrodes. A mathematical model is proposed to determine the reaction and transport between liquid microjets and a reactive solid surface. The conditions were estimated under which oxide depassivation and repassi-vation occur as a function of ultrasonic intensity, surface film thickness, and fluid microjet surface coverage. The model was based on the concept that cavitation induces sufficient momentum and mass transfer rates (water hammer pressures) at a surface to create oxide film stresses leading to depassivation. The model was used in a companion paper (1) to evaluate experimental data on the corrosion behavior of iron in sulfuric acid.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry