There are a seemingly endless variety of cleaning solutions available for us to use in ultrasonic cleaners. Choosing the right one is as important to the ultrasonic cleaning process as the selection of an appropriate temperature and the amount of time the parts will be cleaned.
While we must know exactly what the parts are made of and the types of contaminants we’re removing before we can make a final decision on a cleaning solution, having a general knowledge of the different categories of solutions will get us in the right ballpark so we can fine-tune our selection to meet specific needs. Different cleaning solutions excel at cleaning different types of contaminants in ultrasonic cleaners. Omegasonics explains the different solutions available.
Not all contaminants are removed equally well by all detergents, even when used in ultrasonic cleaners. The substrate, or part, also factors into the type of cleaner that can be used, otherwise, we’d just use the most powerful cleaner we could get our hands on. Seventy percent sulfuric acid may work great at removing scale, but it also removes the carbon steel beneath the scale in short order. Compromises must be made to get the right combination of contamination removal and part protection during ultrasonic cleaning.
Here is a closer look at some of the more common cleaning solutions we use in our ultrasonic cleaners:
Alkaline Solutions – These cleaning solutions typically have a pH of about 11.0, and are usually free of phosphates and caustics. At this lower strength and slightly elevated pH, they are considered “general purpose” cleaners, and do a good job of removing oil, grease, and carbon deposits, in addition to dirt and dust. Some solutions add rust inhibitors to prevent susceptible metals from oxidizing or rusting after we remove them from ultrasonic cleaners.
Acidic Solutions – Cleaning solutions that are acid based typically have a pH of around 4.0, although some go as low as 2.5 to provide effective cleaning. They are mildly effective in removing oil, grease, and cutting fluids, but are best suited for removing scale, oxidation, and tarnish.
Citrus-based Cleaners – One specific type of acidic cleaning solution that deserves special mention are citrus cleaners. It is a mildly acidic formulation that is often also considered to be a general purpose cleaner, yet is excellent at passivating various grades or staninless steel and titanium. Passivation is the process of removing free iron molecules from the surface of these specific metals to create a rust free surface. This process is used extensively in the aerospace, medical and food industries.
Enzymatic Detergents – Enzymatic detergents are ideal for removing protein-based contaminants such as blood, excrement, human tissue, mold, mildew, and bacteria. These solutions are commonly used to clean medical and dental instruments as well as food-grade equipment. This type of solution also does an excellent job of not only removing cutting fluids and oils from parts, but also digesting them so they leave no residue behind in our ultrasonic cleaners.
De-ionized Water – While not specifically a type of detergent or solution, de-ionized (DI) water is nonetheless a phenomenal cleaner for any part that can be exposed to water. DI water will remove surface contaminants, flux residue, some oils, molds, mildews, bacteria, and mineral deposits from parts.