Cleaning Molybdenum

Question:

We have been trying to figure out how to clean molybdenum. Specifically, how to clean the brass deposits from EDM wire and how to clean off the oxide formed when it is exposed to water and air. Can you offer any advice or assistance? D.M.

Answer:

As with most metals, cleaning and oxide removal of molybdenum is done in an acid bath. One formulation that is suggested for the removal of both light and heavy oxide is about 50% (by volume) nitric acid plus about 10% (by volume) hydrofluoric acid (from ASM Handbook Series, Volume 5). The solution should be heated in the range of 120-150F. A mixture of these acids will not only remove the oxides, but will also clean off any residual copper that is picked up from the EDM process. Parts should be rinsed well in water after cleaning (possibly deionized water as a final process step).

These acids require careful handling so all appropriate precautions should be taken. Examples of appropriate safety equipment are (but not limited to), face shield, acid-resistant gloves, chemical-resistant apron and boots as well as very good ventilation. Consult a person knowledgeable in hazardous waste disposal before discarding acidic cleaning solutions or rinses.