Ultrasonic cleaning is favored among all the other cleaning methods because of its versatility, efficiency and thoroughness. In addition, an ultrasonic cleaner is very easy to use as long as you follow a few basic rules, the most important being the one concerning the type of cleaning solution utilized.
Failing to use the right type of solvent might lead to damaged items and to a damaged ultrasonic cleaner tank.
Some basic questions
Before deciding on a specific solution formulation and a supplier, it is best to take some time and analyze a few basic aspects.
First of all, you need to take into account what sort of residue you are trying to remove. There is a difference between removing blood or tissue from medical instruments, clearing of contaminants the best lenses for telescopes and eliminating chips or dust from a machined part.
Secondly, pay attention to the composition of the item you are trying to scrub and how it will interact with the solution. In theory, any object that can be immersed is suitable for ultrasonic cleaning, but a cleaning solvent with the wrong chemical composition may cause damage. For example, a solution formulated with 70% sulfuric acid removes scale, but damages carbon steel.
Finally, are there any more steps after the cleaning process is complete? When it comes to machined parts, maybe they will be subjected to painting or to adding another coating once the parts are cleaned. Surgical instruments have to be sterilized because ultrasonic cleaning does not remove viruses or spores. This aspect must be taken in consideration as well when choosing what type of detergent to use.
These solvents have a pH of 10 or higher – the higher pH the solution has, the more aggressive it is. Depending on how powerful the ultrasonic cleaner is, this type of solution may or may not contain caustic soda (sodium hydroxide).
Moderately alkaline compounds, the ones with a pH ranging from 11.0 to 12.5, are ideal for most metals, including steel (stainless or not), cast iron, zinc, aluminum, brass, copper, and tin. In addition, they also effectively clean glass (including neutral glass), ceramics, and most types of plastic.
Acidic solutions are a bit trickier to use in the sense they are very specific and have to be utilized with suitable materials – some acids might damage certain materials, while the same acids have no effect on others. Knowing which is which is essential for a successful ultrasonic cleaning process.
This type of solvent has a pH of 5.0 or lower, with lower pH solutions being the most aggressive. Acidic solutions are perfect for removing oxidation from almost all metals, providing the solution has inhibitors in order to protect the base material.
Deionized water will work on nearly any material out there, as long as it can be safely immersed in water: glass, metal, epoxies, hard rubber, plastic, just to name a few.
The quantity of deionized water used in the solution has to be calculated carefully because many items will oxidize quickly once taken out of the ultrasonic cleaner tank. In order to prevent this, immediately after the washing process is done, the item has to be placed in a wetting solution and dried. Some of the items that need special post-cleaning handling are switches, printed circuit boards and small servo motors.
High caustic solutions
These solutions are actually alkaline solutions that contain caustic soda. Although they can be used should the need arise, the first option must be more moderate formulated alkaline solvents.
Highly caustic detergents contain hydroxides and silicates and are great for removing oils, wax, or heavy grease from objects made of steel, stainless steel and cast iron. Special attention has to be given to the interaction between magnesium and highly caustic solvents — in case magnesium is added in the ultrasonic cleaner tank, then a low caustic solvent should be used or else it may cause damage to the object.
This type of solution is utilized mostly for cleaning tools and instruments used in medical facilities and in pharmaceutical and food processing industry. It is specially designed to remove contaminants that are based on protein and it is good for brass, titanium, aluminum, stainless steel, but also for lab equipment made of plastic and glass.