machined molybdenum part

[eyalad]

Hi everyone,

I'm looking for recommendations on surface treatments for a machined molybdenum part. Since I don't typically work with molybdenum, I'm unsure of the best approach.

I've come across suggestions for electropolishing and passivation online. Are these methods sufficient for a part that will be used in a clean room environment? Also, could anyone advise on the relevant standards to follow for this application?

Thanks in advance for your help!

 

[Doug Hunter]

What are looking to achieve with the surface treatments, and what is the function of the part?

 

[eyalad]

What are looking to achieve with the surface treatments, and what is the function of the part?

Hi,

Thank you for the reply.

This part will hold a measuring instrument inside a clean room with controlled humidity and temperature.

 

[mfgenggear]

OP
Not enough information.
Is this part
Out in the environment
Near Salt spray,
Specification of the material
Is there galvanic issues
Mixed metal contact
Is it in a oil bath.
And more

 

[eyalad]

OP
Not enough information.
Is this part
Out in the environment
Near Salt spray,
Specification of the material
Is there galvanic issues
Mixed metal contact
Is it in a oil bath.
And more

Is will hold a measuring instrument in a semi conductor clean room.
It will be bolted to an anodized aluminum frame.
Standard grade molybdenum 99.95%

 

[Doug Hunter]

I'm not aware of Molybdenum being used for structural parts, so I don't know why you'd need to coat it. Can you add an explanation of the needed function of the coating? It's not necessarily relevant to your question, but I'm awfully curious why Molybdenum is necessary?

 

[eyalad]

I'm not aware of Molybdenum being used for structural parts, so I don't know why you'd need to coat it. Can you add an explanation of the needed function of the coating? It's not necessarily relevant to your question, but I'm awfully curious why Molybdenum is necessary?

Hi
Due to geometrical constraints, we have some sort of a cantilever. Thin and long. For our application we need minimal bending under load. Imagine a tongue depresser with a load on the end of it.
I just want it look fine and not have any corrosion over time.

 

[Doug Hunter]

I can see that Molybdenum has a high rigidity (elastic modulus), so I understand your selection better. I can't offer any specific surface coating guidance, except to research its reactive properties online.

 

[SWComposites]

How do you get corrosion in a clean room??

 

[mfgenggear]

OP
Never worked with pure moly
so my first look is at a material data sheet.

quote;
IT /MOLYBDENUM/ IS NOT EASILY OXIDIZED BY AIR OR WATER @ ORDINARY TEMP & HAS POOR OXIDN RESISTANCE @ HIGHER TEMP. WHEN HEATED ABOVE 400 °C IT YIELDS A HIGHLY VOLATILE TRIOXIDE (MOO3) AND ABOVE 700 °C OXIDN BECOMES SO SEVERE THAT ITS USE IS POSSIBLE ONLY IF IT IS PROTECTED BY A COVERING LAYER OF AN OXIDN-RESISTANT METAL, AN ALLOY OR DEPOSITION OF SILICON.
Browning, E. Toxicity of Industrial Metals. 2nd ed. New York: Appleton-Century-Crofts, 1969., p. 243
Hazardous Substances Data Bank (HSDB)

​

 

[btrueblood]

You do need to be worried about oxides on the the metal surface, which are quite volatile. Also, the oxides absorb water to a degree, and this water also outgasses.

But, you said clean room, not vacuum chamber, so this may not be a concern. Similarly, if you aren't working at high temperatures (above 180F) then even water volatilitiy is of no concern, and oxide vapors even less concern.

You can't passivate molybdenum, i.e. like stainless steel (companies that advertise passivation don't do a very good job of explaining the process for Mo). You might be able to anodize it, like aluminum. A clear coat paint might be a good choice, or a polymer powder coat.