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Tantalum

One of the most corrosion resistant materials available, exhibits resistance to acid attack comparable to glass.

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, including lithium and sodium-potassium.

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

CORROSION RESISTANCE OF TANTALUM

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

Acetic Acid
20-392° (68-738°F), all concentrations: No attack
Air or Oxygen
At room temperature: practically stable   /   Above 600°C (1112°F): formation of protective surfaces of Ta oxides
Aqueous Ammonia
Practically 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 Monoxide
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 attack   /   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
Beryllia
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