However, if you work with stainless steel components, you know that these alloys are not completely corrosion-proof. Handling damage, contamination and even the act of machining or cutting the steel can compromise the amazingly thin layer that protects the part from rust.
How thin? Try one-ten millionth of an inch thick (0.0000001) which is around 1/100,000th as thick as a human hair. This layer is composed of chromium oxide, and is so thin it literally can’t be seen. The chromium oxide isolates the steel from atmospheric oxygen, preventing it from causing rust. Because the layer forms automatically, in theory it will cover every surface of the component exposed to air.
So, how does the layer become compromised? Mainly through contamination. Any contaminants that contain iron are especially troublesome, because the iron inevitably brings rust with it, and places it in contact with the steel below the layer. Common dirt or shop dust can not only interrupt the layer, but are almost certain to contain some tiny amount of iron. Cutting tools used to machine the steel can leave microscopic bits of their blade surfaces on the part. All these contaminants tend to be invisible to the naked eye.
A sort of contamination can even come from within the steel itself. Some stainless steel contains sulfur added to make the metal easier to machine, and spots where sulfides are exposed at the surface can corrode.
The best way to deliver a part to your customer that will remain corrosion-free is to reestablish the chromium oxide layer with a passivation bath of nitric or citric acid. But prior to that, it’s essential that the part be perfectly clean. For that task there’s no substitute for ultrasonic cleaning. Let’s look at three reasons why:
Hand cleaning is expensive and may not remove all contamination
Instead of paying an employee (possibly a highly paid specialist, such as a machinist) to clean the part, you can place batches of parts in an ultrasonic cleaner and know they’ll be spotless in a few minutes. And since the bubbles from ultrasonic cavitation will reach anyplace liquid will reach, there won’t be any missed spots (or scratches, dings, etc.) due to human error.
Ultrasonic cleaning is excellent for eliminating greases and oils
A common problem in passivation is the presence of cutting oils or other grease on the parts. These will react with the chemical bath, creating bubbles that keep the acid away from the surface and prevent passivation. This can lead to pitting or rusting later on. But an ultrasonic cleaner will remove these oily materials without error.
You can’t afford a contaminated passivation bath
Some contaminants can cause what’s called a “flash attack.” This change in the chemical makeup of the passivation bath causes the surface of the part to be darkened and may also cause etching. The parts will require rework at least, and may be ruined.
To give your customer a corrosion-resistant component they can depend on, you need a cleaning process you can depend on, and ultrasonic cleaning delivers unsurpassed results.
Need more information on the results ultrasonic cleaning can produce in an industrial environment? Click here to learn how Ushers Machine and Tool used ultrasonic cleaning to increase production by 20% while reducing costs. Or see Ultrasonics to the Rescue, a case study of the results Componex saw when they used ultrasonic cleaning to reach grime they couldn’t otherwise clean.