Bill, I am curious about your statement that, "There are electronics (read-sparks) inside." I have never seen an ultrasonic cleaner with sparks flying around, and certainly they don't use sparks in the cleaning process or to generate the sound waves that do the cleaning.
In fact the cleaning liquids I have used are water based, though a water displacing oil (similar to WD-40) should be used after cleaning since the cleaning removes all oil and other protection against rust.
Jim
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