Purity, history, source, and heat-treatment have no apparent influence on the susceptibility of tantalum to hydrogen embrittlement in aggressive reducing acid media. However, contact of tantalum with an extremely small area of platinum appears to be a particularly effective method for preventing embrittlement. Whereas tantalum is embrittled in a few hours in concentrated hydrochloric acid at 190 C (374 F), a system with a tantalum to platinum area ratio of 10,000 to 1 is immune to embrittlement for more than 1000 hours. The corrosion rate of tantalum is not increased by such contact and, in some cases, actually decreases. In addition, the corrosion rate of platinum is reduced to a negligible value by contact with tantalum.
Results of laboratory experiments are described in which tantalum was successfully protected from embrittlement in highly corrosive environments at different temperatures, or under conditions of cathodic charging. The technique is simple, effective, and should find application by expanding the range of environments which can be served by tantalum. 3.2.2, 6.3.13
