Corrosion Rates of Ta and Ta40Nb in Selected Acids

Solution Temp °C Tantalum
10% HNO3 Boiling 104 nil
65% HNO3 Boiling 123 nil
65% HNO3 204 nil
65% HNO3 + 0.01% FeCl3 Boiling 123 nil
10% Formic Acid Boiling nil
10% Oxalic Acid Boiling nil
35% Acetic Acid 177 nil
ASTM G-28-120 hrs 50% H2SO4 + 42 g/l Fe2(SO4)3* Boiling 123 nil
Green Death: welded coupons with crevices in Teflon® washers 100 hrs 12% H2SO4 + 1.2% HCl + 1% FeCl3 + 1% CuCl2* Boiling 101 No crevice attack
40% H3PO4 Boiling 106 —
60% H3PO4 125 —
60% H3PO4 149 —
85% H3PO4 80 nil
85% H3PO4 165 0.3
85% H3PO4 204 3

Corrosion Resistance of Tantalum, Ta2.5W, Ta10W

(Reagent grade chemicals used when appropriate) S = No attack up to 150°C (302°F), or as specified V = Variable depending on concentration and temperature X = Not resistant

Chemical Res. Chemical Res. Chemical Res.
Chemical Res. Chemical Res. Chemical Res.
Acetic acid S Ferrous sulfate S Phthalic anhydride S
Acetic anhydride S Food stuffs S Pickling acids, except HNO3-HF S
Acetone S Fluoride salts V Potassium bromide S
Air,<300°C (570°F) S Formaldehyde S Potassium carbonate V
Air,>300°C (570°F) X Formic acid S Potassium chloride S
Alcohols S Fruits S Potassium dichromate S
Aldehydes S Glycerine S Potassium ferricyanide S
Aluminum chloride S Graphite, <1000°C S Potassium hydroxide, dilute V
Aluminum nitrate S Hydroiodic acid S Potassium hydroxide, conc. X
Aluminum sulfate S Hydrobromic acid S Potassium iodine-iodine S
Amines S Hydrocarbons S Potassium nitrate S
Ammonia V Hydrochloric acid S Potassium permanganate S
Ammonium bicarbonate S Hydrofluoric acid X Potassium pyrosulfate, molten X
Ammonium carbonate S Hydrogen, <300°C (570°F) V Potassium sulfate S
Ammonium chloride S Hydrogen bromide, <400°C S Potassium thiosulfate S
Ammonium hydroxide V Hydrogen chloride, <350°C S Propionic acid S
Ammonium nitrate S Hydrogen fluoride X Refrigerants S
Ammonium acid phosphate S Hydrogen iodide S Sea water S
Ammonium phosphate S Hydrogen peroxide S Silver nitrate S
Ammonium sulfate S Hydrogen sulfide S Sodium acetate S
Amyl acetate or chloride S Hydroxyacetic acid S Sodium aluminate S
Aniline hydrochloride S Hypochlorus acid S Sodium bisulfate, molten X
Aqua regia S Iodine, <300°C (570°F) S Sodium bisulfate, solution S
Barium carbonate S Ketones S Sodium bromide S
Barium chloride S Lactic acid S Sodium carbonate V
Barium hydroxide S Lead salts S Sodium chlorate S
Barium nitrate S Magnesium chloride S Sodium chloride S
Benzoic acid S Magnesium hydroxide S Sodium citrate S
Body fluids S Magnesium sulfate S Sodium cyanide S
Boric acid S Maleic acid S Sodium dichromate S
Bromine, dry, <300°C (570°F) S Manganous chloride S Sodium hydroxide, dilute V
Bromine, wet S Methyl alcohol S Sodium hydroxide, conc. X
Butyric acid S Methylsulfuric acid S Sodium hypochlorite S
Calcium bicarbonate S Milk S Sodium nitrate S
Calcium bisulfates S Mineral oils S Sodium nitrite S
Calcium bisulfites S Mixed acids (sulfuric-nitric) S Sodium phosphate S
Calcium carbonate S Motor fuels S Sodium pyrosulfate, molten X
Calcium chloride S Nickel salts S Sodium silicate S
Calcium hydroxide S Nitric acid S Sodium sulfate S
Calcium hypochlorite S Nitric acid, fuming S Sodium sulfide S
Carbolic acid S Nitric oxides S Sodium sulfite S
Carbon dioxide S Nitrogen, <300°C (570°F) S Sodium thiosulfate S
Chloric acid S Nitrous acid S Stearic acid S
Chlorinated brine S Nitrosyl chloride S Succinic acid S
Chlorine, dry, <250°C (480°F) S Oleum (fuming sulfuric acid) X Sugar S
Chlorine, wet, <350°C (662°F) S Organic chlorides S Sulfamic acid S
Chlorine oxides S Organic acids S Sulfur, <500°C (930°F) S
Chloroacetic acid S Organic esters S Sulfur chlorides S
Chromic acid S Organic salts S Sulfur dioxide S
Chrome plating solutions S Oxalic acid S Sulfur trioxide X
Citric acid S Oxygen, <300°C (570°F) S Sulfuric acid, to 175°C (350°F) S
Cleaning solutions S Pechloric acid S Sulfuric acid, >175°C (350°F) V
Copper salts S Petroleum products S Sulfurous acid S
Dichloroacetic acid S Phenol S Sulfuryl chloride S
Dimethylformaldehyde S Phosphoric acid, S Tannic acid S
Ethylene dibromide S <4ppmF, <180°C Tartaric acid S
Ethyl sulfate S Phosphorus, S Thoinyl chloride S
Fatty acids S <700°C (1290°F) Tin salts S
Ferric chloride S Phosphorus chlorides S Zinc chloride S
Ferric sulfate S Phosphorus oxychloride S Zinc sulfate S

Corrosion Resistance of Tantalum in Liquid Metals

S = No attack up to 150°C (302°F), or as specified
V = Variable depending on concentration and temperature
X = Not resistant

Liquid Metal Resistance
Bismuth to 900°C S
Gallium to 450°C S
Lead to 1000°C S
Lithium to 1000°C S
Magnesium to 1150°C S
Mercury to 600°C S
Potassium to 1000°C S
Sodium to 1000°C S
Sodium-Potassium Alloys to 1000°C S
Zinc to 500°C V
Tin V
Uranium V
Aluminum X

Effect of Platinum on Tantalum Corrosion Resistance and Hydrogen Absorption

Area Ratio Test Period (hrs) Test Environment Temperature Corrosion Rate (mils/year) Hydrogen Absorption (ppm)
Ta 0 96 96% H2SO4 260 27 100
Ta/Pt 165:01:00 96 96% H2SO4 260 15 5
Ta 0 96 36% HCI 190 19 100
Ta/Pt 165:01:00 96 36% HCI 190 6 5