Using De-Ionized Water with an Ultrasonic Cleaning System

Editor’s Note: This article was originally published in October 2017 and has been updated with new information and reposted in September 2023.

Ultrasonic cleaning is a powerful and versatile method for removing contaminants from a wide range of materials. It is widely used in the automotive, electronics, medical, and manufacturing industries. The cleaning fluid plays an essential role in this process, and using de-ionized water can significantly improve the performance of an ultrasonic cleaning system.

De-ionized (DI) water is a preferred choice for many ultrasonic cleaning applications. What makes DI water stand out, and when should you use it? This article explains how de-ionized water affects ultrasonic cleaning, when it is appropriate to use it, and how it can improve cleaning for specific parts and devices.

What Is De-Ionized Water?

De-ionized water is water that has been purified to remove ion contaminants. These ions typically include minerals such as calcium and magnesium, which are common in tap water.

To produce DI water, first filter the water to remove organic matter. It is then passed through an ion exchange bed. Standard filtration cannot remove dissolved substances such as salts, because they form ions in the water that are too small to filter out. The ion exchange resins attract and remove these dissolved ions, and the resulting water is far purer than ordinary tap water. Removing these ions has significant benefits for ultrasonic cleaning.

Do You Need De-Ionized Water? Choosing the Right Cleaning Fluid

The right cleaning fluid depends on the part being cleaned and on how heavily it is contaminated:

• Ordinary water: often enough for lightly contaminated parts, or for durable parts that can withstand the aggressive cleaning action of low ultrasonic frequencies.
• Water with a mild detergent: effective for more heavily contaminated parts, and for fragile parts that can tolerate detergents.
• De-ionized water: the best way to speed up cleaning and ensure even, complete results on delicate parts that cannot tolerate detergents.

Heating the cleaning solution, or adding solvents or detergents formulated for a specific contaminant, can further improve results. The best combination depends on the parts and on the type of contamination.

Benefits of De-Ionized Water for Ultrasonic Cleaning

Enhanced Cleaning Performance

DI water can improve the cleaning performance of ultrasonic cleaning systems. This is especially important when cleaning delicate parts that cannot tolerate detergents. Because DI water contains no ions, it absorbs ionized compounds and dissolved contaminants more readily, which speeds up cleaning. In some applications, an ultrasonic cleaning tank with a heater that warms the DI water makes cleaning even more effective.

Improved Rinsing

After ultrasonic cleaning, rinse parts to remove any remaining cleaning solution. Rinsing with ordinary water can leave traces of salts, mineral spots or organic films on parts as the water evaporates. DI water contains no impurities, so it evaporates without leaving residue and produces clean, spot-free parts.

Detergent Efficiency

When you use a mild detergent in ordinary water, impurities in the water use up some of the detergent’s cleaning power before it reaches the contamination on the part. DI water contains no impurities to weaken the detergent, so its full cleaning power goes toward removing contaminants from the part’s surface.

When to Use DI Water

DI water is recommended for delicate parts that detergents could damage, such as semiconductor wafers, printed circuit boards, and medical devices. It helps the ultrasonic cavitation bubbles clean more quickly without relying on detergents as the cleaning agent.

DI water alone is not effective at removing stubborn grease and oil. In those cases, use a mild detergent or a solvent that dissolves the specific contaminant without damaging the part. DI water remains valuable for the final rinse, and it improves the effectiveness of any detergent used during cleaning.

Application Examples

Machined and metal parts. Machined components and metal parts often carry metallic dust on their surfaces. The microscopic cavitation bubbles produced by ultrasonic cleaning dislodge these particles, and DI water quickly absorbs any metallic ions that dissolve into the solution. These applications benefit from DI water and typically do not require detergents or heating.

Engine parts with oil and grease. Engine parts are often coated with oil and heavy grease. Heating the cleaning solution softens these deposits, and a mild detergent helps dissolve the oil and grease. Using DI water as the solution base makes the detergent more effective.

Plastic parts, circuit boards, and semiconductor and medical components. These parts may be contaminated with organic residue. A detergent can help remove it, but some parts, such as printed circuit boards and medical components, are sensitive to detergents. In these cases, solvents may not be used, or they may be limited to specialized detergents that dissolve organic matter without harming the underlying material. DI water does not remove the organic residue directly, but it improves the performance of the detergents that do.

Kaijo’s Expertise in Ultrasonic Cleaning Systems

With over 65 years of experience in ultrasonic cleaning technology, Kaijo offers expert consultation on using ultrasonic cleaning systems. Our team can help determine whether DI water is right for your application. Kaijo can supply individual ultrasonic cleaning components or complete turnkey systems, and our in-house expertise ensures recommendations are tailored to each customer’s cleaning requirements. We can also help you select the right ultrasonic frequencies and configure your system.

Using de-ionized water in an ultrasonic cleaning system can improve cleaning, especially for delicate parts. Combined with the right detergents or solvents, it can significantly increase cleaning efficiency. Contact us for a complimentary consultation about ultrasonic cleaning for your application.