Degreasing
Trichlorethane, perchlorethane and similar solvents may be used to degrease niobium (Caution: Use only ventilated hoods). Mind that chlorinated hydrocarbons form a fix chemisorptive compound with niobium and can hardly be removed completely.
Pickling
As the first step of cleaning oxidized niobium surfaces, These are very stable and therefore difficult to remove but can be treated with acidic or alkaline pickling media. The entire process must be kept under constant control and under the conditions described in the following two paragraphs, otherwise the basic metal could be attacked strongly.
Alkaline Pickling
Oxide layers are removed by dipping the metal into molten sodium hydroxide (NaOH) containing up to 10% sodium nitrite (Na NO₂) by weight. Temperature should be below 400℃ (673K), thin wire and pieces of thin section should remain no longer than two minutes in the hydroxide. Cooling and rinsing with water are followed by acidic pickling.
Acidic pickling
Light or invisible oxide layers on niobium canbe removed by acidic pickling. The following mixture is recommended. 4parts by volume HF (70% by weight), 8 parts by volume HNO₃ (70% by weight), 1 part by volume H₂SO₄ (87% by weight) and 0-8 parts by volume H₂O.
Afterwards, parts should be thoroughly rinsed with water.
Electropolishing
Niobium can be electroplished anodically in a mixture of 28 volume percent HF (40%), 38 volume percent H₃PO₄ (85%), 34 volume percent H₂SO₄ (90%) and an addition of 1 litre of H₂O in which 0.5g N-(n-hexadecyl-)-pyridinium bromide-monohydrate is dissolved. The current density is approximately 10 A/dm² and the temperature of the electrolyte about 20 to 25 ℃ (293-298k). It is recommended that the parts to be polished in the electrolyte are moved.

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