Tantalum and niobium have exceptional passivity in almost all environments and under almost all conditions. Both materials are easily worked and fabricated with high room temperature ductility. On the practical scale of passivity, tantalum lies within the range of the noble metals and can be substituted for them in many applications. Niobium is less expensive and more widely available but is somewhat less corrosion resistant than tantalum (although still considerably more so than most other metals). Both metals are effectively resistant to pitting corrosion in chloride, bromide and iodide at high potential and, consequently, find effective use as anodes. Fluorides are likely the only species in aqueous environments to which neither tantalum nor niobium have any significant resistance. Also, their high temperature oxidation resistance is poor. This article summarizes the behavior and corrosion-related applications of these remarkable elements.