How to Use an Ultrasonic Cleaner to Strip Paint from Complex Parts

October 3rd, 2011

An ultrasonic cleaner can help here.

An ultrasonic cleaner can help here.

A quality restoration job may call for repainting complex cast, machined or formed metal parts to return them to a “like new” condition.  Removing old paint is part of the process, but unless an ultrasonic cleaner is used to tackle the job, manual paint removal could be the longest time-consumer in the entire project.  Moreover, anyone who has used harsh paint-removal solvents knows how unpleasant the task can be.  Dealing with the remover, the fumes, the glop and the frustrations of getting into cracks, crevices and other tight spots is not fun.

Let Ultrasonic Cleaner Cavitation do the Dirty Work

Ultrasonic cleaners such as the Elmasonic E series available from Tovatech come in several sizes and are equipped with timers and temperature controls.  They hold from less than a gallon to more than 7 gallons of ultrasonic cleaning solution.  This means you can purchase a cleaner that suits the size of the jobs you undertake.  Small or large, the cleaning principle is the same.  

Ultrasonic transducers powered by the unit’s ultrasonic generator create millions of microscopic bubbles that implode on contact with parts immersed in the solution.  So violent is this implosion (It has been calculated that temperatures in excess of 10,000°F and pressures in excess of 10,000 PSI are generated at the implosion sites) that it literally blasts away paint and other contaminants. But because the implosion is so fast it does not damage surfaces.   As an added benefit the bubbles are so small they are able to penetrate cracks, crevices and blind holes impossible to reach by hand. 

Selecting an Ultrasonic Cleaning Solution

Nearly all of today’s ultrasonic cleaning solutions are biodegradable – including those that work best for paint removal.   At Tovatech we recommend a semi-aqueous, micro-emulsion formulation called CLN-STR7-5.  Add it full strength to the ultrasonic cleaner and start cleaning after the solution temperature has reached about 70˚C.  Cleaning time will vary depending on the size of the piece and amount of paint to be removed.  A nice feature of this formulation is that it can be reused after you filter it through a cloth.

Other possibilities are CLN-LR201 (with ammonia) and CLN-LR110 (ammonia free). These are a concentrated and should be diluted with seven parts of water to one of concentrate.  Although the ammoniated product is the stronger of the two it will produce an odor at elevated temperatures.  Provide ventilation.  Set the solution temperature to <40˚C for ammoniated and 50˚C for non-ammoniated solutions.

Each paint removal task may be different. Some cycles may take longer than others depending on what you’re working on.  After some experimenting with solutions and times you’ll soon become an expert. 

Ultrasonic Cleaning Preparation and Maintenance

Elmasonic E ultrasonic cleaners come with detailed instructions.  All fresh ultrasonic cleaning solutions should be degassed to remove entrapped air before you start the cleaning cycle.  This is accomplished by operating the filled unit without a load for about 40 minutes or until air bubbles stop rising to the surface.

When you are ready to remove paint scrape away loose or blistered particles.  Set the ultrasonic cleaner thermostat and allow the solution to reach the recommended temperature.  The Elmasonic E series units will start automatically when the temperature is reached (or you can start them manually).  Place the parts in the basket in a way they do not contact each other, lower the basket into the solution and cover the unit with the supplied lid.  At the end of the cycle remove the basket, rinse the parts and inspect to be certain the paint is removed satisfactorily.  They should be dried before repainting.

When the solution no longer cleans effectively it should be changed.  Dispose of it along with accumulated paint residue according to local regulations.  Take the time to clean the tank following the manufacturer’s recommendations before refilling it with fresh solution.

If you do a lot of paint stripping you’ll find that the Elmasonic E ultrasonic cleaner will soon pay for itself in terms of time saved and increased throughput.  Contact the ultrasonic cleaning experts at Tovatech for added information on selecting and using an ultrasonic cleaner.

How do you remove paint from metal parts?


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