LEAFITOUT, you are wrong. I want to listen to sound advices and answers to my question, which in particular was how to remove the white powder-like stuff from inside the instrument. It was a technical question basically addressed to the technicians who worked with the instruments. I have never seen something like that in my practice. It was not concerned any legal issues or FAA rules.
The CMM for the instrument usually has a section on cleaning, if it doesn't you need to contact the manufacturer for advice. If it is corrosion i'd suggest a strip down to see what is corroding before the problem turns into a more expensive one.
