molybdenum and fuming nitric acid

We are working with moly furnace components at the moment. We were under
the assumption that moly was unaffected by strong acids, yet, when we
immersed our pure moly sample in fuming nitric acid, it rapidly
developed a loose dark red deposit. Given that we are immersing the
components in 1600 deg C Calcium fluoride, we want to avoid nasty
suprises, like the moly is impure in some way.
I would be very grateful for any comments on just what we have seen. Is
it a moly oxide of some kind ? Moly Trioxide of course is clear/white.
Thanks for any help.
Steve Taylor
Reply to
Steve Taylor
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Bruce Craig's "Handbook of Corrosion Data" (ASM International 1989) says on page 378 that: "molybdenum is rapidly attacked by oxidizing agents such as nitric acid".
L. L. Shreir's "Corrosion" (2nd ed., Butterworths,1976), says that (P 5.15): "Molybdenum exhibits good reisistance to hydrochloric, hydrofluoric, phosphoric, and sulfuric acids....It is rapidly attacked by oxidizing acids such as nitric acid, and by reducing acids containing oxidizers such as HNO3, FeCl3, etc."
Similar information can be turned up via a Google search too of course.
Why are you using nitric acid?
Pittsburgh Pete
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Reply to
Pittsburgh Pete
Thanks for that - The acid was being used to see if my material was pure - I am not a chemist, I am the engineer who designed the apparatus. It was my supposedly expert customer who suggested nitric as a kind of assay, since he didn't believe the metal was pure.
Reply to
Steve Taylor

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