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Ultrasonic Cleaning Rinsing Options

Rinsing parts after an ultrasonic cleaning cycle can be an extremely critical operation.

There are many industries where cleaning procedures specify more than one rinse cycle and may also include ultrasonic rinsing in order to meet strict cleanliness standards. In such cases distilled water and deionized (DI) water are often used as ultrasonic cleaning rinsing options to remove all traces of cleaning solution residues after parts are removed from the cleaning bath.

Spot-free drying is the main benefit of both distilled and DI water rinses vs. rinsing with regular water. This is because they contain no dissolved minerals to remain as residues when products dry.

Among products calling for thorough rinsing are included precision electronic components, PCBs, precision optics and surgical instruments. (In contrast, no rinsing or plain water rinsing suffices for parts where residues have no effect on performance.)

Distilled or DI, what is the Difference?

Explaining the difference between distilled and DI water can become quite complex.Several web sources are available, but here is a brief description of each.

Distilled water is produced by boiling water and collecting the condensate, with minerals remaining behind. The process is energy intensive in terms of boiling the water and may not result in a completely satisfactory product for ultrasonic rinsing. Although distillation removes nonvolatile materials, certain oils and other volatile organic materials may distill with the steam and remain in the condensed water.

Deionized water is produced when water flows through a column of ion exchange resins that exchange negative and positive ions in the water for H+ and OH- ions that combine to form deionized water. While the process removes ions remaining organic molecules and microorganisms must be removed through additional steps.

A characteristic of deionized water is that it wants to return to its “natural” state by absorbing ions from most any source including metal containers and even the surrounding air. This characteristic, while challenging, is why DI water is so effective for rinsing after ultrasonic cleaning cycles. Because of its tendency to absorb ions DI water is shipped and stored in plastic containers to minimize ion absorption. Plastic piping is employed to deliver DI water to rinsing stations.

Reverse Osmosis Water

A third rinsing option, reverse osmosis (RO) water is produced by forcing water through a semi-permeable membrane that allows water molecules to pass while holding back most ions. The membrane also holds back most microbes and organic contaminants that may remain in DI water. If ions and organic contaminants are of concern a solution can be a combination of RO and DI purification processes.

An Elma ultrasonic cleaning and rinsing station

Which Rinsing Option to Use?

Good question. The answer depends on how you define “clean.” Then you can determine which rinsing option is the best. Professional and trade associations often have ultrasonic rinsing recommendations that may include multiple rinse cycles.

Although iUltrasonic does not offer distilled, DI or RO water for rinsing, our scientists will be glad to help you make a decision based on your cleaning requirements. Give us a call at 973 440-2191


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