How to Remove Rust With an Ultrasonic Cleaner
With time and exposure to the elements, rust is inevitable on 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. Rather than dispose of these pieces as unusable, a good cleaning in an ultrasonic cleaner can help redeem them.
Rust needs a bit of a vigorous cleaning hence you need a good quality ultrasonic cleaner. By this we mean that it should be one that can run for at least half hour. Once you have this cleaner in hand, the rest is easy. All you need to do is wipe off loose rust fragments from the surface of the piece. 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 distribute the sound field uniformly throughout the medium, and then drop in the pieces to be cleaned. Run the machine for around half hour.
Scores of microscopic bubbles are created in an ultrasonic cleaner through alternating waves of expanded and compressed ultra sound. This process is called cavitation. The expansion cycle causes bubble formation while compression causes the implosion. This implosion releases a highly energetic, microscopic liquid stream that strikes the surface of the object being cleaned, dislodging the dirt stuck to it.
The ultrasonic cleaning process is able to do what manual cleaning cannot hope to achieve and that too with less effort and half the time it would take. In microscopic level, the process will actually show you a vortex being formed in the middle of the bubble. Fact is, ultrasonic cleaning is the only recourse when you have objects 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 session. 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. Having said that, ultrasonic cleaning rarely makes this necessary. Whenever possible, do not take 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. While water can be used for cleaning, it is usually advisable to use a surfactant that will bind with the dirt at the molecular level. Detergent powder is a common surfactant but for ultrasonic cleaning it is better to choose a solution that is compatible with your type of object. In the case of rust acidic solutions are usually best. The pH level should be around 2 to 4. However, you need to weigh this in the light of what other metals and non metals comprise your object. For example 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 care must be taken with 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.
