Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

The authoritative public forum
  for Metal Finishing since 1989
  

Stripping/Cleaning Molybdenum base parts

Q. One of our customers has sent us parts to be cleaned and stripped.

As this is a new process, we are limited in explaining the exact nature of the parts themselves, so please bear with me.

• We have a molybdenum base that is coated with a very thin layer of titanium.
• We have a molybdenum base with a very thin layer of tantalum.
• And finally, we have a molybdenum base with a very thin layer of titanium tungsten.

Using Nitric acid is absolutely unacceptable as it turns the moly brown.

Using hydrofluoric acid causes a chemical (toxic fumes) reaction with both the tantalum and titanium.

Any ideas? Any and all input is greatly appreciated.

Cleaning Pure Molybdenum

Q. We design and manufacture mass spectrometers. One of these instruments is a Quadruple mass spectrometer. The mass filter in this instrument is a set of 4 rods made from high purity (99.95 % pure) molybdenum. They are approximately 12 mm in diameter and about 131 mm long. I am looking for a procedure that will clean the molybdenum the will remove the metallic impurities that get embedded on the surface during the fabrication of these parts.

These rods are centerless ground and then lapped to the final dimensions.

Any help would be greatly appreciated.

2002

"Extractive Metallurgy of Molybdenum"

on AbeBooks

or Amazon

(affil links)

A. How deep are these impurities? My recommendation is electropolish to final dimension. You may need to build a tuned cell to get the final dimension accurate, depending on specs.

Dave Kinghorn
Chemical Engineer
SUNNYvale, California

Cleaning arsenic-contaminated molybdenum parts

Q. We have a number of molybdenum parts contaminated with deposited arsenic. The moly is thin, say 25 thou. We need to remove the arsenic without affecting the moly. Any help would be appreciated.

Cheers

Descaling Molybdenum

Q. We are currently using a molten caustic descaling process to descale molybdenum rods and plates. Does anyone have any alternative descaling techniques. High pressure spraying has been suggested.

Electropolishing of cross sectional embedded Molybdenum foil

Q. I want to have some info w.r.t electropolishing of cross-sectionally embedded Mo foil of 127 micron thickness. I tried sulfuric acid + methanol [affil links] (87.5% methanol + remaining 1N H2SO4) at room temp using S.S cathode and epoxy embedded foil as anode. I am getting brown deposition on to the sample after cleaning with water. A blue-black passive film is forming and still it is not appearing electropolished. Will adding hydrogen peroxide help?
Please Let me know,

Molybdenum and hydrocarbons

Q. Hello,

Can anyone let me know if Moly can make contact with Hydrocarbons? I have heard that this can cause issues with the surface of the moly. Hydrocarbons in question are - Isopropanol and Paraffin.

A. Hi Ben,
As you probably know, moly substrates form a strong oxide layer on the surface at room temperature. The oxide layer should not be harmed by IPA. Paraffin, in liquid form, will adhere to moly as the liquid cools but it can be blasted off, butned off in a furnace or otherwise removed. Assuming r.t., 1 atm in air.

Blake Kneedler
Feather Hollow Eng. - Stockton, California
December 26, 2017

Electropolishing of Molybdenum and alloys

Q. We are going to establish a tensile test laboratory, the material of tensile test sample is mainly Mo, W, Ta alloy.
Test sample should be rectangular shape, about 2 mm thickness, 50 mm length and 6 mm width with shape according to ASTM E8 (plate).
Before testing, we need to electro-polish the tensile test sample for better surface finish.
Just want to know: