By means of cavity effects of ultrasonic

acid washing passivation solution can generate a bundle of dense explosion on surface of the castings at pulling force of ultrasonic wave beam

which can activate the acid washing passivation process

resulting in not only passivating casting but also making surface of castings more smooth and delicious. The activation of acid-washing-passivating solution can greatly decrease acid-consumption rate and proportion as well as viscosity

which results in easy recovery and full utilization of resource

decreasing the product cost. In addition

waste castings resulting from over-corrosion during acid washing process was eliminated

and acid-fog was also relieved to some extent.