The ultrasonic cleaner solution you select plays a major role in successful ultrasonic cleaning operations. Ultrasonic cleaner solutions are available in a wide variety of formulations – each designed for specific cleaning tasks. These solutions are also referred to as cleaning chemistries and in some cases “soaps.” We’ll stick with ultrasonic cleaner solution in this post and provide you with tips on how to make the right selection.
How an Ultrasonic Cleaner Solution Works
Regardless of the chemistry, an ultrasonic cleaner solution works by a process called cavitation. This is defined as the implosion of millions of microscopic vacuum bubbles in an ultrasonic cleaner’s tank filled with the solution. Bubbles are created by generator-powered transducers vibrating at ultrasonic frequencies such as 37,000 cycles per second (37 kHz).
When bubbles contact products to be cleaned they implode violently (but safely) against all wetted surfaces to blast loose and carry away contaminants.
Further details on how this equipment works is found in our post on how to select an ultrasonic cleaner.
With this behind us we get into the purpose of this post.
What is the Contaminant?
What is the contaminant? Put another way, what do you want to remove by an ultrasonic cleaning process? Examples include
- grease, grime and grit on engine and drive train components
- salt and other residues on scuba gear
- soldering residues and other contaminants on PCBs
- burned on deposits on plastic injection molds
- grit and grime on cherished vinyl LP records
- contaminants on surgical and dental instruments
- tarnish or old paint on brass, copper and other surfaces
- finger prints and other soils on optics
- grinding, polishing and lapping media on fabricated parts
- powder residues and other contaminants on firearms
What is the Nature of the Contaminant?
Do you want a demulsifying or emulsifying cleaning solution formulation? This distinction deals with what happens to the contaminants, particularly greasy contaminants, as they are removed by the cleaning process.
Demulsifying ultrasonic cleaner solutions cause oily contaminants to float to the surface of the cleaning solution. This makes them easy to skim off either manually or via spray bars and weirs for storage and later disposal.
The step serves two purposes:
- it reduces the potential for floating contaminants to adhere to the product when it is removed from the bath
- it helps prolong the useful life of the ultrasonic cleaning solution. Demulsifying formulations are typically used in high-volume cleaning operations.
Emulsifying formulations hold contaminants in suspension.
These ultrasonic cleaner solution formulations are used for low-volume cleaning operations.
Because contaminants remain in the solution rather than float to the top they build up over repeated cleaning cycles, begin to inhibit cleaning efficiency and, perhaps more important, may remain on the surfaces of cleaned products. This could necessitate post-cleaning rinsing operations.
Hard particles such as chips, fines, shavings and plain old dirt fall to the bottom of the cleaning tank. These must be removed each time the solution is changed, otherwise they can over time damage the tank bottom. Tank cleaning recommendations are provided in user manuals.
What Do You Want to Clean with Ultrasonic Cleaning Solution?
What is being cleaned? Most anything that can be safely wetted can be cleaned using ultrasonic energy. As a few of many examples, ultrasonic cleaner solution formulations are designed for iron and steel castings, fabricated parts, plastics, precious metals, ceramics, glass, rubber, and polished surfaces such as aluminum. Note that chromium-plated products should not be cleaned ultrasonically.
What if any are the steps that follow cleaning?
- nothing – clean and reinstall
- rinsing – may be required to remove solution residues
- total absence of residues – i.e. surgical implants, similar products
- surface protection – i.e. temporary rust protection
- professional association or government agency recommended steps
Steps for Rinsing Ultrasonic Cleaner Solution Steps
Post-cleaning rinsing steps can include washing with a water spray and immersion in an ultrasonic rinsing tank. These are used to flush away any residuals remaining due to what is called “drag out.”
Products that are painted, plated or powder coated are prime candidates for thorough post cleaning rinsing to ensure proper adhesion of the coating to the surface.
Which brings up yet another point: rust. Since the vast majority of these solutions are water based (and some specifically formulated to remove rust), rust inhibitors should be added either to the solution or to the rinsing tank.
Elma KS, available from Tovatech as a mildly alkaline concentrate, provides temporary corrosion protection on a molecular level.
A Closer Look at Ultrasonic Cleaner Solution Chemistry – What is pH?
What is pH? Wikipedia defines pH as a measure of hydrogen ion concentration; a measure of the acidity or alkalinity of a solution. … Aqueous solutions at 25°C (77⁰F) with a pH less than seven are acidic, while those with a pH greater than seven are basic or alkaline
Although there are exceptions ultrasonic cleaner solutions can be divided into three basic chemistries based on their pH: alkaline, acidic and neutral.
The following paragraphs provide selected examples of cleaning solution chemistries. Ask the Tovatech scientists for recommendations that satisfy your particular requirements.
When to Specify an Acidic Ultrasonic Cleaner Solution
Acidic cleaning solutions are exemplified by elma tec clean S1 with a pH of 1.6 in concentrate form. Recommended dilution is to 1 to 5% with water.
It is used to remove corrosion and lime deposits, water damage, grease, oil and oxide layers from non-ferrous and light metals as well as PCBs, glass, plastics, tarnished brass and copper.
Stronger acidic solutions are also available for these materials along with nonferrous heavy metals, stainless steel, and cast iron. As noted above, surfaces subject to rusting should include elma KS in the cleaning or rinsing tank for temporary corrosion resistance.
An important caution: Stainless steel ultrasonic cleaner solution tanks must be protected when using corrosive low pH solutions such as nitric, sulfuric, formic, or hydrofluoric acid. This is accomplished by using a plastic insert along with other precautions described in our post on safely cleaning with acid.
Alkaline Ultrasonic Cleaner Solutions
A highly popular alkaline cleaning solutions is demulsifying elma tec clean A4 with a pH of 13.4. It is widely used in labs and workshops. Diluted to 1 to 5% with water it removes grease, oils, soot, wax, combustion residues, and organic contaminants from engine parts, all metals, glass, ceramics, plastics and rubber.
A slightly milder alkaline formula is emulsifying elma tec clean A1 with a pH of 10.8. Use it for removing light oils, fluxing agents, dust, grease and fingerprints from PCBs, electromechanical devices, electronics and fine optics. Recommended dilutions are to 3 to 10% with water.
Ammonia-containing elma tec clean A2 is an alkaline solution used to remove grinding, polishing and lapping media, grease and oil from nonferrous metals, precious metals, brass and copper. Its ammonia content leaves a bright shiny surface on brass and copper products. With a pH of 11, it is diluted to 5 to 10% with water.
When to Select a Neutral Ultrasonic Cleaner Solution
An example of a neutral cleaning solution is elma tec clean N1 with a pH of 9.3 diluted to 2 to 5% with water.
Neutral cleaning solution formulations are recommended for gentle cleaning action on highly sensitive products to remove oils, grease, grinding and polishing media, dust and fingerprints.
Other applications include ceramics, precious metals and jewelry. (Note that certain gemstones should not be subjected to ultrasound, in which case N1 can be diluted to 10% with tap water and stones slightly swirled in the mixture.)
Another example of a neutral cleaning solution formulation is foam-inhibited elma clean 260 dip & splash that can be used either in an ultrasonic bath diluted to 2%, or for spray cleaning (1%) with tap or deionized water.
This formula is suitable for metallic surfaces including aluminum and light metal alloys as well as for glassy, ceramic and mineral surfaces. It removes aqueous cooling emulsions from mechanical treatments, deposited lime soaps and other contaminants.
Ultrasonic Cleaning using Volatile Solvents
In certain instances a volatile solvent such as IPA, acetone or toluene is recommended for ultrasonic cleaning operations.
IPA, for example, is used for cleaning medical instruments and surgical implants; acetone is a great solvent for degreasing and cleaning, both for the same reasons: they do not leave solution residues on parts being cleaned.
Requirements for cleaning with volatile solvents include the use of explosion proof ultrasonic cleaners located in an area where there are no ignition triggers from nearby electrical systems. When operating an explosion-proof ultrasonic cleaner you create what is called a National Electric Code hazardous location due to fumes given off and the possibility of spilled solvent.
A Wrap-up on Selecting Ultrasonic CleanerSolutions
We’ve touched on but a few examples of ultrasonic cleaner solutions available to solve virtually any cleaning challenge.
Tovatech’s scientists are ready to assist you in selecting the correct formulation for your operations – as well as the ultrasonic cleaning equipment that does the job most efficiently.
Call or chat with us for unbiased help in selecting equipment, cleaning solution formulations and operating procedures that will help you do the job quickly and efficiently.
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