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Corrosion resistance of tantalum to water, aqueous solutions and non-metals

Tantalum is a sensible choice whenever high corrosion resistance is required. Tantalum is often compared to the precious metals because it is resistant to all types of chemical substance. However, in thermodynamic terms, tantalum is a base metal which can nevertheless form stable compounds with a wide variety of elements. When exposed to air, tantalum forms a very dense oxide layer (Ta2O5) which protects the base material from aggression. This oxide layer therefore makes tantalum corrosion-resistant.

At room temperature, the only inorganic substances that tantalum is not resistant to are: concentrated sulfuric acid (H2SO4), fluorine (F), hydrogen fluoride (HF), hydrofluoric acid (HF) and acid solutions containing fluoride ions (F-). Alkaline solutions (OH-), molten sodium hydroxide (NaOH) and potassium hydroxide (KOH) also attack tantalum. In contrast, the material is resistant to aqueous ammonia solutions. If tantalum is exposed to chemical aggression, hydrogen enters its metal lattice and the material becomes brittle. The corrosion resistance of tantalum falls gradually with increasing temperature.

Tantalum is inert in contact with many solutions. However, if tantalum is exposed to mixed solutions, its corrosion resistance may be impaired even if it is resistant to the individual components taken separately. 

Corrosion resistance to water, aqueous solutions and non-metals

Water

Hot water < 150 °C

resistant

Inorganic acids

Hydrochloric acid < 30 % up to 190 °C
Sulfuric acid < 98 % up to 190 °C
Nitric acid < 65 % up to 190 °C
Hydrofluoric acid < 60 %
Phosphoric acid < 85 % up to 150 °C

resistant
resistant
resistant
not resistant
resistant

Organic acids

Acetic acid < 100 % up to 150 °C
Oxalic acid < 10 % up to 100 °C
Lactic acid < 85 % up to 150 °C
Tartaric acid < 20 % up to 150 °C

resistant
resistant
resistant
resistant

Lyes

Sodium hydroxide < 5 % up to 100 °C
Potassium hydroxide < 5 % up to 100 °C
Ammonia solutions < 17 % up to 50 °C
Sodium carbonate < 20 % up to 100 °C

resistant
resistant
resistant
resistant

Saline solutions

Ammonium chloride < 150 °C
Calcium chloride < 150 °C
Ferric chloride < 150 °C
Potassium chlorate < 150 °C
Body fluids < 150 °C
Magnesium sulfate < 150 °C
Sodium nitrate < 150 °C 
Tin chloride < 150 °C

resistant
resistant
resistant
resistant
resistant
resistant
resistant
resistant

Non-metals

Fluorine
Chlorine < 150 °C
Bromine < 150 °C
Iodine < 150 °C
Sulfur < 150 °C
Phosphorous < 150 °C
Boron < 1 000 °C

not resistant
resistant
resistant
resistant
resistant
resistant
resistant


Feel free to contact us: molly@samaterials.com

Keywords: Tantalum,Ta2O5,Corrosion Resistant


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