DIY Home Improvement

Rust formation is inevitable on most metal surfaces. It could affect parts of your car’s carburetor, tools you are working with, small spare parts you keep for a rainy (sic!) day and other similar 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 and your ultrasonic cleaner needs to be better than the low end models. 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 simple. All you need to do is wipe off loose fragments of rust from the surface of the piece. Plug in the ultrasonic cleaner; fill the tank to the prescribed level with an appropriate cleaning solution. Switch it on for a while to disperse the sound field throughout the medium, and then drop in the pieces to be cleaned. Let it operate for around half hour.

Scores of microscopic bubbles are generated 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, dislodging the dirt stuck 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. Ultrasonic cleaning is in fact the only recourse when you have objects with intricate structures and complex geometries that are hard or impossible to reach with manual tools.

Take a look at the pieces once the cleaning cycle is done. In case of really stubborn rust stains, it may be necessary to operate another cycle. If you still find small pockets of rust after the second round, you may have to sandpaper it manually. This 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, spray on an anti-rust primer to protect the surface.

The kind of cleaning solution you use to clean rust is extremely important. 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 suited for your type of object. In the case of rust acidic solutions are usually best. This would mean that its pH level would have to be 2 to 4. However, you need to consider 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 take extra precaution for objects that are made up 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.