When nickel, titanium or zirconium alloys are not enough...

Tantalum lock nuts are best known for its unmatched corrosion resistance and chemical inertness. Tantalum nuts have a similar corrosion resistance to that of glass, but all of the typical mechanical and electrical properties of a metal.

Tantalum lock nuts are also extremely stable at high temperatures, since tantalum has a melting point around 3000°C. High temperature applications require vaccum or inert gas since tantalum may embrittle when used in oxygen rich environments above 250°C.  Tantalum nuts are also one of the most bio-compatible metals available and is also radio-opaque due to its high density (16.68 g/cm3).

All tantalum lock nuts are available in commercially pure tantalum and tantalum 2.5% tungsten (Ta-2.5%W).

Contact us to see if your required tantalum lock nuts are in stock and how our engineers may help you with your tantalum fastener application.

ResourcesTantalum Torque Spec


Tantalum Locknut Features and Beneifts

A tantalum locknut resists loosening from vibrations and torque. One of the most common styles is a prevailing torque locknut. This kind of tantalum locknut has a prevailing torque feature which deforms elastically, preventing it from freely spinning like a standard nut.

The two most common and reliable forms of prevailing torque locknuts are the flexloc style and the polymer insert lock nut. A tantalum flexloc nut is all-metal in composition with a segmented collar that creates six “locking fingers,” that act as a spring. Tantalum polymer insert lock nuts are often referred to as nylon insert locknuts, although various high performance polymers can be used for the screw threads to “bite into.” Both flexlock and polymer insert locknuts are available in both hexagonal and 12 point configurations.

All Metal Flexloc Lock NutFlexloc Lock Nut Insert Lock NutPolymer/Nylon Insert Lock Nut
  • Can be used at high temperatures
  • Distributes load evenly due to the fact that it is manufactured as one solid piece.
  • Is THE most reliable all-metal self-locking nut.
  • As it is all metal, it is best for high temperature or corrosive applications
  • One of the only all-metal lock nuts that is certified to 15 cycles of prevailing torque – which is military standard.
  • Overall the most reliable locknut, with the only limitation of application temperature
  • Best for low temp applications, typically less than 350°F
  • Various polymers inserts available (Nylon, Vespel, PVDF, etc.) for higher temp. or corrosive applications.
  • Excellent reusability – can reliably be re-used 15 times
  • Eliminates galling and cold-welding common with exotic alloys

Other all metal lock nuts available include the tantalum stover and elliptical styles. Though these styles are often a cheaper initial cost, they are less reliable than the flexloc style. As these styles delivering less prevailing torque cycles and often result in more failures, the flexloc style is a better investment for both reliability and cost savings.

Tantalum Grades, Specifications and Chemistry

Tantalum (Commercially Pure)

Commercially pure tantalum metal is 99.95% pure tantalum has some o the best corrosion resistant properties of any metal. While its corrosion resistance is exceptional, it is relatively soft and mechanically similar in strength to copper.

Tantalum Specifications: UNS R05200, ASTM B521, B708

Tantalum Chemistry

Tantalum 2.5% Tungsten (Ta-2.5W)

This grade of tantalum alloyed with 2.5% tungsten provided better overall strength while maintaining its exception corrosion resistant properties. For tantalum fastener applications this is usually preferred.

Tantalum 2.5% Tungsten Specifications: UNS R05252, ASTM B521, B708

Tantalum 2 5 Tungsten Chemistry


Physical Properties

  • Density 16.6 g/cc
  • Melting Point 3290 K, 2996°C, 5462°F
  • Boiling Point 5731 K, 6100°C, 9856°F
  • Coefficient of Thermal Expansion (20°C) 6.5 x 10(-6) / °C
  • Electrical Resistivity (20°C) 13.5 microhms-cm
  • Electrical Conductivity 13% IACS
  • Specific Heat .036 cal/g/°C
  • Thermal Conductivity .13 cal/cm(2)/cm°C/sec

Tantalum Tensile Data

Tensile Data


Tantalum Iso-Corrosion Curves

Specialty Metal H2SO4 Iso-Corrosion Curve

Specialty Metal HCl Iso-Corrosion Curve

Tantalum Corrosion Resistance Table


For all temperatures up to at least 302F (150C) unless otherwise indicated 

Acetic acid
Acetic anhydride
Air,<300°C (570°F)
Aluminum chloride
Aluminum nitrate
Aluminum sulfate
Ammonium bicarbonate
Ammonium carbonate
Ammonium chloride
Ammonium nitrate
Ammonium acid phosphate
Ammonium phosphate
Ammonium sulfate
Amyl acetate or chloride
Aniline hydrochloride
Aqua regia
Barium carbonate
Barium chloride
Barium hydroxide
Barium nitrate
Benzoic acid
Body fluids
Boric acid
Bromine, dry, <300°C (570°F)
Bromine, wet
Butyric acid
Calcium bicarbonate 
Calcium bisulfates
Calcium bisulfites
Calcium carbonate
Calcium chloride
Calcium hydroxide
Calcium hypochlorite
Carbolic acid
Carbon dioxide
Chloric acid
Chlorinated brine

Chlorine, dry, <250°C (480°F)
Chlorine, wet, <350°C (662°F)
Chlorine oxides
Chloroacetic acid
Chromic acid
Chrome plating solutions
Citric acid
Cleaning solutions
Copper salts
Dichloroacetic acid
Ethylene dibromideEthyl sulfate
Fatty acids
Ferric chloride
Ferric sulfate
Ferrous sulfate
Food stuffs
Formic acid
Graphite, <1000°C
Hydroiodic acid
Hydrobromic acid
Hydrochloric acid
Hydrogen bromide, <400°C
Hydrogen chloride, <350°C
Hydrogen iodide
Hydrogen peroxide
Hydrogen sulfide
Hydroxyacetic acid
Hypochlorus acid
Iodine, <300°C (570°F)
Lactic acid
Lead salts
Magnesium chloride
Magnesium hydroxide
Magnesium sulfate

Maleic acid
Manganous chloride
Methyl alcohol
Methylsulfuric acid
Mineral oils
Mixed acids (sulfuric-nitric)
Motor fuels
Nickel salts
Nitric acid
Nitric acid, fuming
Nitric oxides
Nitrogen, <300°C (570°F)
Nitrous acid
Nitrosyl chloride
Organic chlorides
Organic acids
Organic esters
Organic salts
Oxalic acid
Oxygen, <300°C (570°F)
Pechloric acid
Petroleum products
Phosphoric acid, <4ppmF,<180°C
Phosphorus, <700°C (1290°F)
Phosphorus chlorides
Phosphorus oxychloride
Phthalic anhydride
Pickling acids, except HNO3-HF
Potassium bromide
Potassium chloride
Potassium dichromate
Potassium ferricyanide
Potassium iodine-iodine
Potassium nitrate
Potassium permanganate

Potassium sulfate
Potassium thiosulfate
Propionic acid
Sea water
Silver nitrate
Sodium acetate
Sodium aluminate
Sodium bisulfate, solution
Sodium bromide
Sodium chlorate
Sodium chloride
Sodium citrate
Sodium cyanide
Sodium dichromate
Sodium hypochlorite
Sodium nitrate
Sodium nitrite
Sodium phosphate
Sodium silicate
Sodium sulfate
Sodium sulfide
Sodium sulfite
Sodium thiosulfate
Stearic acid
Succinic acid
Sulfamic acid
Sulfur, <500°C (930°F)
Sulfur chlorides
Sulfur dioxide
Sulfuric acid, to 175°C (350°F)
Sulfurous acid
Sulfuryl chloride
Tannic acid
Tartaric acid
Thoinyl chloride
Tin salts
Zinc chloride
Zinc sulphate


Air,>300°C (570°F)
Ammonium hydroxide
Fluoride salt
Hydrofluoric acid

Hydrogen, >300°C (570°F)Hydrogen fluoride
Oleum (fuming sulfuric acid)
Potassium carbonate
Potassium hydroxide, dilute

Potassium hydroxide, conc.
Potassium pyrosulfate, molten
Sodium bisulfate, molten
Sodium carbonate
Sodium hydroxide, dilute

Sodium hydroxide, conc.
Sodium pyrosulfate, molten
Sulfur trioxide
Sulfuric acid, >175°C (350°F)

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