Structure and Corrosion Behavior of Cold-Sprayed Tantalum Coatings

Cold spraying enables the production of pure and dense metallic coatings with low porosity and low oxygen content, capable of, e.g., resisting corrosion. Furthermore, denseness (impermeability) plays an important role in the corrosion resistance of tantalum coatings, and good corrosion resistance is based on the formation of a protective oxide layer. The aim of this study was to investigate the microstructure, denseness, and corrosion behavior of high-pressure cold-sprayed tantalum coatings by a conventional scanning electron microscope (SEM) and a field-emission scanning electron microscope (FEG-SEM). Various corrosion studies (e.g., salt spray fog tests and electrochemical studies) were taken to gain information on the corrosion properties of the coatings in the different aqueous solutions. The microstructural studies showed the high denseness of coatings due to the fact that interfaces in the coatings were practically free of voids or other imperfections. The cold-sprayed tantalum coating showed excellent corrosion resistance: in microstructural analysis, it showed a uniformly dense microstructure, and, in addition, performed well in all corrosion tests.