ONE OF THE MOST CORROSION RESISTANT MATERIALS AVAILABLE, EXHIBITS RESISTANCE TO ACID ATTACK COMPARABLE TO GLASS.

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.

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
  • Recrystallization Temperature 900˚C–1200˚C

GENERAL CORROSION RESISTANCE

Tantalum is one of the most corrosion resistant ductile metals exhibiting resistance to mineral acids except hydrofluoric 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.

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