Why is niobium resistant to corrosion at ordinary temperatures?

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niobium processing Four one-millimetre thick samples of niobium metal foil.

Niobium is highly resistant to corrosion at ordinary temperatures due to the formation of a protective oxide layer on its surface. This passive film acts as a barrier, preventing further chemical attack by the environment. While the metal maintains this excellent resistance under standard conditions, it becomes susceptible to oxidation when exposed to temperatures above approximately 400°C (750°F).1

Beyond its general corrosion resistance, niobium is also notable for its stability in specific demanding environments, such as its resistance to corrosion by molten alkali-metal coolants, which makes it a valuable material for use in nuclear reactor cores.1