Basic Concerns with Ultrasonic Cleaning | Part 3: Cleaning Fluid
Ultrasonic cleaning is a versatile method for precision cleaning a broad range of objects. While it involves a simple process, there are several factors to consider for ensuring the best results. In this series of blogs, we’re examining seven key factors that can impact ultrasonic cleaning.
In this article, we look at cleaning fluid (also known as detergent, soap, or cleaning solution) and discuss the part it plays in the ultrasonic cleaning process.
Why Use an Ultrasonic Cleaning Fluid
To understand why you need to use a cleaning fluid in an ultrasonic cleaner, it’s helpful to know about the chemical processes involved.
Ultrasonic cleaners create sound waves that move through a liquid causing microscopic bubbles to form and burst in a process called cavitation. As the bubbles burst, high-speed jets of liquid hit a target object, removing contaminants from the surface of the object.
A detergent is a surfactant, which means it lowers the surface tension of water when it’s mixed with it. Detergent molecules contain both hydrophilic (water-loving) and hydrophobic (water-hating) parts. When a detergent is added to water, contaminants – like oil or grease – are attracted to the hydrophobic parts of the cleaning solution, making them easier to remove.
Using dish soap with a brush or cloth speeds up the process of cleaning dishes. In the same way, using a specially designed detergent in an ultrasonic cleaner makes the cleaning process quicker and more effective. The detergent loosens the contaminants on items to be cleaned and enables the ultrasonic system to increase the cavitation forces.
Choosing the Right Ultrasonic Cleaning Fluid
Alkaline Detergents
With a pH between 10 and 12.5, moderate to high alkalinity detergents can be used to remove a wide variety of contaminants from many types of materials. For example:
- Materials: ferrous and non-ferrous metals, glass, plastics, ceramics, painted surfaces, and composites
- Contaminants: grease, carbon, coolants, dirt, oils, cutting fluids, lubricants, buffing compounds
Highly caustic solutions with a pH of 14 can be used if more aggressive cleaning is required, for example, to remove rust or strongly adhered contaminants. These solutions aren’t suitable for metals such as magnesium and aluminum but can usually be used on steel, stainless steel, and cast iron.
Acidic Detergents
Acidic cleaning fluids have a low pH and contain phosphoric acid. They are used for applications such as polishing instruments, cleaning electronic parts, and removing oxides or mineral deposits such as limescale.
Great care must be taken with acidic cleaning solutions as they can damage the items being cleaned and even the ultrasonic cleaner itself. Some solutions contain inhibitors to prevent damage to materials such as brass, copper, and aluminum. Specially designed solutions can also be used on stainless steel, bronze, plastics, glass, and ceramics.
Enzymatic Solutions
Enzymes are catalysts that break down organic materials such as blood and starches. Solutions containing enzymes are often used in the pharmaceutical and food industries to remove organic contaminants from objects.
Amylase enzymes are used on starches and carbohydrates. Proteolytic enzymes help remove salvia, blood, and other proteins.
Deionized Water
Most ultrasonic cleaning applications require some type of cleaning fluid for maximum efficacy. However, in some cases – such as with delicate materials or very light soiling – it’s acceptable or even advisable to use deionized water.
Solvents
Petroleum-based solvents are effective cleaners. They can quickly dissolve residues such as grease, oil, grime, and carbon build-up. Solvents don’t usually need to be rinsed off and they evaporate quickly, making the whole cleaning process faster than with aqueous solutions.
However, solvents contain volatile organic compounds (VOCs), which are dangerous to health and the environment, particularly when used in vapor cleaners. Disposing of solvents after use is hazardous and expensive.
Read more about the benefits of using aqueous cleaning solutions with ultrasonic cleaners
Ultrasonic cleaners can be designed to use solvents safely for those applications where only solvents are capable of meeting the cleaning requirements.
Using the Ultrasonic Cleaning Fluid
When you’ve selected the right cleaning fluid for your application, you need to follow the product guidelines to get the best results from your ultrasonic cleaning process.
Cleaning Fluid Concentration
Cleaning fluids often need to be diluted and mixed thoroughly for maximum effect and to prevent damage to the items being cleaned.
Operating Temperature
Operating at the right temperature for your chosen cleaning fluid is the factor with the biggest impact on the cleaning process. For alkaline cleaning solutions, a temperature of 140°F is optimum for the chemical process. Some fluids with a higher pH require higher temperatures.
Cleaning Time
Cleaning times vary depending on several factors, including the type of object, levels of contamination, and strength of the cleaning solution. Some objects may need a pre-cleaning cycle for maximum effect.
Soaking, Rinsing and Drying
Soaking isn’t required for most ultrasonic cleaning applications, but objects with strongly adhering contaminants may benefit from a pre-soak before the cleaning cycle starts.
Most objects need to be rinsed following ultrasonic cleaning with a detergent or cleaning fluid, with immersion or spray rinsing (or both).
Some materials need to be dried as soon as cleaning is complete to prevent oxidation.
Safety
Most ultrasonic cleaning solutions are caustic or acidic and could cause harm to workers and damage to some materials. It’s important to adhere to all instructions, such as wearing protective equipment, working in well-ventilated areas, and diluting cleaning fluids before use.
Wrapping Up
Using the right cleaning fluid in the right way is a critical factor to gain the best results from ultrasonic cleaning.
UPC provides a range of detergents for use with ultrasonic power cleaners and guidance on how to choose the best one for your requirements.
If you have more questions, please feel free to get in touch and send in samples so we can determine the right cleaning fluid for you. And look out for the next post in this series in which we explore how the position of the transducer affects the cleaning process.
Ultrasonic Cleaners for Rent
We offer a range of our most popular ultrasonic cleaners for rent on a 30-day try-before-you-buy basis or as a long-term rental option.