Ultrasonic Rust Removal

Q. What ultrasonic frequency is best for removing corrosion on stainless steel?—O.T.

A. Most often, rust removal is accomplished with the use of an acid cleaner or, occasionally, strong alkaline cleaners. Generally, ultrasonics alone in a simple medium of water would not be sufficient to remove most rust deposits. Ultrasonic solutions are more effective when used after they have been “degassed” which involves boiling or heating the solution above the operating temperature of the bath. This is because the dissolved gases in a bath can lower the effectiveness of the ulatrosonic cavitations.

Based on this, I would not recommend the use of an ultrasonic bath if you are using an acid cleaner to remove the rust residues. The acid cleaner will generate a certain amount of hydrogen gas at the part surface that would decrease the efficiency of the ultrasonic process. An alkaline cleaning process would not have the same surface reactions, so you would find the use of ultrasonics more effective. If using ultrasonics to provide a boost to the rust removal process, I would expect a lower frequency to have more energy to remove some of the rust. I would recommend a frequency in the range of 20-40 kHz.