Q. Corrosion resistance of tantalum?

Tantalum is readily attacked by strong alkalis, even at room temperature, and therefore, is not suitable for use in processes where the pH levels can vary significantly on either side of neutral.

Tantalum is highly corrosion resistant to all concentrations of H2SO4 up to 98%, even at elevated temperatures. However, within the 60 to 70% concentration range above 300°F (150°C) and above the 98% concentration, the corrosion rate increases, but is uniform and, therefore, tantalum can still be used in some applications. Some studies have shown that the addition of nitrate ion (NO₃^-)_ to H₂SO₄ significantly reduces the rate of corrosion of tantalum up to 475°F (220°C).

When connected to a less noble material in a corrosive environment, tantalum will behave cathodically in the galvanic cell. If corrosion takes place at the less noble material, the presence of atomic hydrogen may be absorbed by the tantalum and cause hydrogen embrittlement.

Tantalum is extremely reactive, particularly at temperatures above 600°F (320°C). Great care must be taken to prevent contamination from oils, foreign debris and non-inert gases.