Tantalum, limitations from corrosion

Corrosion resistance. The corrosion resistance of niobium is more limited than tantalum, and this must be taken into consideration. The limitation stems from its sensitivity to most alkalies and certain strong oxidants. However, niobium is totally resistant to such highly corrosive media as wet or dry chlorine, bromine, saturated brines, ferric chloride, hydrogen sulfide, and sulfur dioxide as well as nitric and chromic acids. It is also resistant to sulfuric and hydrochloric acids within specific temperature and concentration limits. 

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