Corrosion Properties of Cold-Sprayed Tantalum Coatings
Cold spraying enables the production of pure and dense metallic coatings. Denseness (impermeability) plays an important role in the corrosion resistance of coatings, and good corrosion resistance is based on the formation of a protective oxide layer in case of passivating metals and metal alloys. The aim of this study was to investigate the microstructural details, denseness, and corrosion resistance of two cold-sprayed tantalum coatings with a scanning electron microscope and corrosion tests. Polarization measurements were taken to gain information on the corrosion properties of the coatings in 3.5 wt.% NaCl and 40 wt.% H2SO4 solutions at room temperature and temperature of 80 °C. Standard and improved tantalum powders were tested with different spraying conditions. The cold-sprayed tantalum coating prepared from improved tantalum powder with advanced cold spray system showed excellent corrosion resistance: in microstructural analysis, it showed a uniformly dense microstructure, and, in addition, performed well in all corrosion tests.
Keywordscold spraying corrosion properties microstructure tantalum
We thank Mr. Werner Krömmer, of Linde AG Gas, for the spray coatings and for his valuable advice. We also thank Dr. Karri Osara, of Outotec Research Oy, for organizing chemical analysis of the powders. This study was funded by Finnish Funding Agency for Technology and Innovation (TEKES) and a group of Finnish industrial companies.
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