Electrodeposition of Tantalum Coatings on Nitinol Stent and Composition of Intermetallic Compounds Forming During Electrolysis

Abstract

The electroreduction of tantalum complexes in a chloride-fluoride melt was studied on tungsten, and nitinol electrodes. It was found that on a nitinol electrode in addition to the peak associated with the discharge of fluoride tantalum complexes, several peaks on the voltammogram related to the formation of intermetallic compounds of nickel and tantalum were observed. The electrodeposition of tantalum coatings from the NaCl-KCl-NaF(10 wt.%)-K2TaF7(10 wt.%) melt onto nitinol stent was investigated. The formation during electrolysis of several intermediate layers between the deposited layer and substrate was found and their microstructure and chemical composition were determined. It was determined that the surface layers of the nitinol are depleted in titanium due to corrosion in the melt. During electrodeposition a barrier intermetallic layer TiNi2.4Ta0.6 is formed, which prevents the penetration of tantalum into the substrate, but does not prevent the diffusion of nickel and titanium from the substrate into the deposited layer of tantalum.