I have tried to use 1.5% citric acid solution (plus a little detergent) for the cleaning of regulator parts in the ultrasound cleaner. I have set the concentration so that the pH is roughly equivalent to the 2.5% acetic acid solution that is normally used. I expected the citric acid to behave the same as the vinegar, but without the smell. Near to those places however where the plating was damaged originally, and a lot of green corrosion product was visible, the dissolved copper cemented on the surface of the intact chrome plating. The cementing itself is not very surprising based on the standard potentials of the metals involved, however I have never seen it this obviously when I was using acetic acid. Maybe the reason is that the acetic acid removes the protecting oxide layer from the top of the chrome plating, activating the chromium, but before I go into more wild speculation, I would like to ask whether anyone else has seen this phenomena with any kind of cleaning solution? Or maybe this is only the result of the excessive amount of corrosion products?