Polishing of Zirconium Metal

I would like to ask about some process to polish the Zirconium metal. In fact, I have recently made few Zirconium crucibles and during the making of these, the metal color has changed to dark brown. I will be thankful if someone could help me with these.

Can't give you a really good answer about polishing unless more is known about the present surface finish and the size of the parts. How rough is it? Also, the color change sounds as if you are getting a chemical reaction. That can be caused by a liquid or gas in the environment or process.

I have polished zirconium metal. Using a ceramic belt sander ( my piece is flat) I went from 80 grit to 220 grit.

then go to an orbital sander from 200 to 1000 grit using carbide sanding paper.

then use polishing wheel with various compounds.