Molybdenum News Center

How to Remove the Oxide Layer of Molybdenum Rod?

Molybdenum rod is a rod-shaped product made from high quality molybdenum powder and gains characteristics of high melting point, good thermal conductivity and low thermal expansion from molybdenum metal itself. Even in high temperature, it can resist oxidation and has high strength. 

Because of high melting point of molybdenum metal itself, moly rods are widely machined into electrodes, screws, heating elements, connectors for high temperature furnaces, stir rods for rare earth smelting industry, and bulb holders in the electric lighting industry.

There are four surface conditions for this product: 

1. Sintered: its surface shows silver-gray metallic. 　　

2. Forged: there is a layer of oxide on the surface with black color. 

3. Grounded: forged moly rods are machined with smooth and metallic luster surface. 

4. Polished: surface is very smooth after machined. 

The surface of forged rods is allowed to have oxide file and slight traces after forging and grounded or polished ones shall be anti-oxidation. All surfaces should be no delamination, cracks, burrs and longitudinal cracks and other defects.

However, although molybdenum metal can resist high temperature, its products exposed to the air at room temperature will still oxide slightly. How to remove oxide layer on the surface? 

In addition to the most common method of alkaline cleaning, acid pickling is another effective method to clean metal bars. Here I recommend a solution for everyone: 50% nitric acid by volume mixes with 10% hydrofluoric acid by volume. The temperature during the cleaning process must be controlled between 102 and 150 degrees Fahrenheit. This mixed pickling can not only effectively remove the oxide layer on the molybdenum rods, but also remove the copper left on the product during the EDM process. After pickling, molybdenum products must be washed repeatedly in clean water.

Since the mixed acid is a high-risk item, strict protective measures should be taken in all cleaning steps. Appropriate safety equipment during cleaning includes masks, acid-resistant gloves, chemical-resistant aprons and boots should be equipped and the working environment should be in very good ventilation.

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