Rust formation is inevitable on most metal surfaces. This could be on parts of your car’s carburetor, small spare parts you keep, tools you are working with and other such objects. Instead of thinking to dispose them, a good cleaning in an ultrasonic cleaner can help redeem them.

Rust needs a bit of a vigorous cleaning and your ultrasonic cleaner needs to be better than the low end models. Your cleaner should be one that is able to operate for at least half hour. Once you’ve figured the ultrasonic cleaner model that you want to use, the rest is easy. You only need to wipe off loose fragments of rust from the surface of the material. Plug in the ultrasonic cleaner; fill it to prescribed capacity with the cleaning solution specific to the material being cleaned. Switch it on for a while to disperse the sound field throughout the liquid, and then drop in the pieces to be cleaned. Run the machine for around half hour.

Scores of microscopic bubbles are produced in an ultrasonic cleaner by alternating ultrasound waves of compression and expansion. This process is called cavitation. The bubbles are formed during the expansion cycle and implode during the compression cycle. A highly energetic liquid stream is released upon implosion, which strikes the surface of the object being cleaned, dislodging the contaminants that adhere to it.  

The ultrasonic cleaning process is able to do what seems impossible if cleaning manually and that too in half the time and effort it would take. A microscopic view of the process will actually show you a vortex being created in the middle of the bubble. Fact is, ultrasonic cleaning is the only recourse when you have items or materials with intricate structures and complex geometries that are hard or impossible to reach with manual tools.

Once done, take a look at the pieces. In case of really stubborn rust stains, you may need to put it through another cycle. If small pockets of rust are still visible, you may have to sandpaper it manually. This solely depends on the piece being cleaned, its tolerance for abrasive treatment compared to a gentler ultrasonic action. But this stage is rarely necessary. As far as possible, avoid taking an abrasive material to rust surfaces. After the cleaning, make sure you spray on an anti-rust primer to protect the surface.

It is extremely important that a right cleaning solution is used. Plain water can be used for cleaning, but it is advisable to use a surfactant that will bind and ultimately remove the dirt. Detergent powder is a common surfactant but for ultrasonic cleaning it is better to choose a solution that is suited for your type of object. In the case of rust acidic solutions are advised. The pH level should be around 2 to 4. However, you need to weigh this in the light of what other compounds are present in your object. If your object contains both plastic parts, as well as aluminum surfaces either disassemble the piece or manually remove as much rust as possible and then use a milder cleaning solution.  

Ultrasonic cleaners are ideal for rust removal though take extra precaution for objects that are composed of more than one material.

This article was written by Dr. Bob Sandor, a Director at Tovatech, a leading North American supplier of ultrasonic cleaners. When not busy running his company, he explores his fascination with the many aspects of various scientific & industrial devices. For more information on this article visit the Tovatech site from any of the above links.