How to Safely Clean with Acid in an Ultrasonic Cleaner

An Elma ultrasonic cleaner with an acid-resistant plastic tub insert
An Elma ultrasonic cleaner with an acid-resistant plastic tub insert

There is a wide variety of ultrasonic cleaning solutions on the market – each formulated for specific cleaning operations in an ultrasonic cleaner.  These solutions are generally classified as alkaline (high pH), neutral, or acidic (low pH).  Most acidic ultrasonic cleaning solution concentrates are biodegradable and when diluted according to instructions can be used in stainless steel ultrasonic cleaning tanks such as the Elmasonic series available from Tovatech.

Protecting Staff and Ultrasonic Cleaner Tanks from Highly Acidic Baths

There are exceptions, and an important one is if you must use corrosive low pH solutions such as nitric, sulfuric, formic, or hydrofluoric acid in an ultrasonic cleaner.  Without proper protection these solutions can wreak havoc on your ultrasonic cleaner and the investment it represents.

Solving this problem is twofold and while relatively simple requires a procedure that must be part of your company’s operations manual.  The first is being certain you have an air handling system that draws off fumes emanated during the ultrasonic cleaning cycle.  The second is protecting the tank itself from the acid.

The stainless steel ultrasonic cleaning tank is protected by an acid-resistant plastic tub insert to hold the acidic cleaning solution.  Tubs are sized according to the capacity of the ultrasonic cleaner tank and because of that they are smaller that the tank dimensions.  When you select a tank make sure your largest parts will fit in the tub.

5 Steps to Ultrasonic Cleaning with Acidic Solutions

  1. The bottom of the plastic tub must not be in contact with the bottom of the stainless steel tank and there must be space between the side walls of the two containers.  A properly sized tub will solve this.
  2. Add water to the ultrasonic tank so that the tub is in contact with water when positioned in the tank.  The rim flange of the tub rests on the rim of the tank.  Never turn on the ultrasonic power when the tank is dry.
  3. Place a lid on the tub and turn on the ultrasonic cleaner to allow the water and acidic cleaning solution to degas.  Some cleaners such as the Elmasonic S units have an auto degas feature to remove cavitation inhibiting air in the water and solution.   Cavitation action by the ultrasonic transducers will pass through the water, through the plastic tub and into the cleaning solution.
  4. Objects to be cleaned should be carefully positioned on the bottom of the tub or in baskets then lowered into the cleaning solution.  You will get optimum cleaning if they do not contact each other.  Set the heater and timer as appropriate for parts being cleaned.
  5. At the end of the cleaning cycle carefully remove and rinse the parts.

Disposal of spent cleaning solutions should be in accordance with local regulations.

Remember that the plastic tub insert absorbs some of the ultrasonic power.  This must be taken into account when selecting an ultrasonic cleaner.  Contact the ultrasonic cleaning professionals at Tovatech for expert advice on cleaning equipment, solutions and processes.

About Rachel Kohn

So how did an MIT Ph.D. end up selling refrigerators? When I figured out that a lot more scientists buy lab refrigerators than innovative leading-edge instruments. I hope that my many years of lab experience will help you find the right equipment for your work. Before co-founding Tovatech I worked in business development and project management at Smiths Detection, Photon-X, Cardinal Health, and Hoechst Celanese. And before that I spent 12 years as an R&D chemist at Hoechst Celanese and Aventis working on advanced drug delivery systems, polymer films and membranes, optical disks, and polysaccharides. Some day, eventually, I’ll make enough money to develop an innovative technology that will change the world. Read More