Alkali Salts, Organics, and Other Media

Tantalum is not attacked by dry salts or salt solutions at any temperature or concentration unless hydrofluoric acid is liberated when the salt is dissolved or strong alkali is present. Salts which form acidic solutions, such as ferric chloride, have no effect on tantalum. However, fused sodimn or potassium hydrosulfate dissolve tantalum.  

Most organic compoimds, including acids, alcohols, ketones, alkaloids, salts, and esters, have no effect on tantalum. Specific exceptions should be made for chemicals that may hydrolyze to free fluoride ion or contain (or liberate) sulfur trioxide or strong alkali. One other exception is worthy of note. Mixtures of anhydrous methanol with chlorine, bromine, or iodine cause a pit-type corrosion on tantalum at 65°C. ° This observation is imusual because tantalum is imattacked by either methanol, the halogens alone, or the reaction product, methyl halide, even at somewhat higher temperature. Furthermore, pit-type corrosion is rarely observed with tantalmn. It was concluded that the strong corrosive attack of mixtures of methanol and halogens on tantalum depended on the formation of a haloformic add intermediate. 

Tantalum is completely inert to body fluids and tissues. Bone and tissue do not recede from tantalmn, and this biocompatibility makes it an attractive material for body and dental implants. However, the superior strength and rigidity of stainless steel and titanimn and the castabUity of high-cobalt alloys have led to their greater use for prosthetic devices. Tantalmn has nevertheless been used for bone replacement and repair, for cranial repair plates, suture wire, and wire gauze for abdominal muscle support in hernia smgery.  

At red heat tantalum reacts with sulfur or hydrogen sulfide to form tantalum sulfide (Ta2S4). At lower temperatures the metal is completely inert. In like maimer, at elevated temperatures on the order of at least 800°C, tantalum powder or shavings react with elemental carbon, boron, and silicon to form the corresponding binary compoimds. Tantalum also reacts with vapors of phosphorus, selenium, and tellurium at comparable temperatures. In contrast, there is only slight attack on the metal by liquid selenides and tellurides of the rare earths and uranium in the range 1300-2100°C, and tantalum is considered a satisfactory material for handling these intermetallic compoimds. 

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