Tantalum corrosion characteristics

Corrosion resistance of tantalum in hydrochloric acid at various concentrations and temperatures. (From General Technologies Corporation. Tantalum, Corrosion Data, Comparative Charts and Coating Characteristics, A subsidiary of cities service corporation.)... 

The most common types of resistor material are nichrome (NiCr) and tantalum nitride (TaN). Although NiCr has excellent stability and TCR characteristics, it is susceptible to corrosion by moisture if not passivated by sputtered quartz or by evaporated silicon monoxide (SiO). TaN, on the other hand, may be passivated by simply baking in air for a few minutes. This feature has resulted in the increased use of TaN at the expense of NiCr, especially in military programs. The stabihty of passivated TaN is comparable to that of passivated NiCr, but the TCR is not as good unless annealed for several hours in a vacuum to minimize the effect of the grain boundaries. Both NiCr and TaN have a relatively low maximum sheet resistivity on alumina, about 400 S2/ for NiCr and 200 / for TaN. This requires lengthy and complex patterns to... 

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