Tantalum


What's This?

Tantalum owes its corrosion resistance to a tenaciously adherent oxide film akin to the entire family of passive, reactive metals. The metal has gained acceptance for use in electronics, missile technology, the chemical industry and the medical field. Tantalum is immune to attack by many acids and salt solutions. It is, however, subject to hydrogen embrittlement in alkaline solutions. It is used to fabricate heat exchangers, reaction vessels, bayonet heaters, thermo wells, surgical implants and radiation shielding. Tantalum should not be used in air at temperatures above about 300°C because of severe oxidation.

Properties

Tantalum is one of many transition elements located in group 5 of the periodic table. It is a gray, heavy metal and is very corrosion resistant.
Atomic No. 73
Atomic Wt. 180.9479
Specific Gravity 16.654
Melting Point 2996˚C
Coefficient of Thermal Expansion 6.5 X 10-6/°K
Specific Heat 0.033 cal/g/°K
Ultimate Tensile Strength (Room Temperature, Annealed) 41 ksi
Yield Tensile Strength (Room Temperature, Annealed) 25 ksi
Poisons Ratio 0.35
Modulus of Elasticity 27 X 106 psi
Recrystalization Temperature 900˚C–1200˚C

General Corrosion Resistance

Tantalum is one of the most corrosion resistant ductile metals exhibiting resistance to mineral acids except hydroflouric acid, acid solutions containing fluoride ions, or free sulfur trioxide and is embrittled by alkaline materials. It is resistant to many molten metals; lithium and sodium-potassium <1000˚C, uranium <1400˚C, zinc <450˚C and bismuth <500˚C. The temperature limit for use in air is about 250˚C to 300˚C. In vacuum, or inert atmosphere, tantalum can be used at temperatures over 2000˚C.

This data is based on laboratory testing only. Your in-plant results may differ. Testing is recommended under other conditions as needed.

Corrosion Resistance Tables

Tantalum's resistance to corrosion by many materials is expemplified in the following Corrosion Resistance Table.

Corrosion Resistance of Tantalum
SUBSTANCE
   REACTION
Acetic Acid
  

20-392° (68-738°F), all concentration: No attack
Air or Oxygen
   At room temperature: practically stable
Above 600°C (1112°F): formation of protective surfaces of Ta oxides
Aqueous Ammonia
   Proactically no attack
Aqua Regia
   Cold and hot: practically no attack
Carbon (Graphite)
   At high temperatures: carbide formation
Carbon Dioxide
   Above 1200°C (2912°F): oxidation
Carbon Monoxied
   At red heat: reaction (absorption of C and O)
In high vacuum above 1400°C: formation of CO
Chromic Chloride Acid
   20-100°C (68-212°F), concentrated: no attack
Aqueous Caustic
   Cold: practically stable
Hot: noticeable attack
Molten Caustic
   Stable
Chlorine
   at 250°C (464°F): beginning attach
Above 450°C (842°F): violent reaction
Ferric Chloride
   19°C (66°F) Boiling, 5-30% concentration: no attack
Hydrocarbons
   Above 800-1000°C (1472-1832°F): carbide formation
Above 1400°C (2552°F): complete carburizing
Hydrochloric Acid
   Cold and Hot: no attack
Hydrofluoric Acid
   Strong Attack
Hydrofluoric and Nitric Acid
   Rapid dissolution
Hydrogen
   Above 300-400°C (572-752°F): formation of hydride
Above 1000°C (1832°F): very slight solubility of hydrogen
In high vacuum above 600-700°C (1112-1292°F): evolution of hydrogen
Hydrogen Peroxide
   Concentrated: good resistance to attack
Hydrogen Sulfide
   At red heat: sulfide formation
Nitric Acid
   Cold and Hot: no attack
Nitrogen
   Up to 150°C (302°F): no attack
Above 800°C (1472°F): nitride formation
Oxalic Acid
   20-96°C(68-205°F), saturated: no attack
Phosphoric Acid
   85% concentration, 145-210°C (293-410°F): no attack
Potassium Hydroxide
   110°C (230°F), 5% concentration: no attack
Sodium Hydroxide
   100°C (230°F), 5% concentration: no attack
100°C (230°F), 40% concentration: rapid attack
Steam
   at red heat: rapid oxidation
Sulfur Dioxide
   Up to 300°C (572°F): stable
Sulfuric Acid
   Cold and hot: no attack
Molten Metals:
    
Sodium
   Up to 1200°C (2192°F): resistant
Magnesium
   Up to 1150°C (2102°F): resistant
Lithium, Potassium, Lead
   Up to 1000°C (1832°F): resistant
Bismuth
   Up to 900°C (1652°F): resistant
Mercury
   Up to 600°C (1112°F): resistant
Zinc
   Up to 500°C (932°F): resistant
Gallium
   Up to 450°C (842°F): resistant
Refractory Oxides:
    
Alumina
   Up to 1900°C (3452°F): stable
Beryilla
   Up to 1900°C (2912°F): stable
Magnesia
   Up to 1800°C (3272°F): stable
Zirconia
   Up to 1600°C (2912°F): stable
Thoria
   Up to 1900°C (3452°F): stable
   
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