Ensinger, Wolfgang ; Flege, Stefan ; Baba, Koumei (2012)
Platinum implantation into tantalum for protection against hydrogen embrittlement during corrosion.
In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 272
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

Platinum is well known for its catalytic activity, even in small quantities. Among others, it catalyzes the recombination of hydrogen atoms to molecules and the desorption of the molecules from a surface. This favourable feature can be used to protect metals from detrimental hydrogen incorporation. This may take place in the case of tantalum when it corrodes in strong acids. Tantalum is a highly inert metal which can be used for devices and vessels for acid handling. When it is exposed to concentrated sulphuric acid, its corrosion rate is acceptably low. However, a side reaction may become problematic. When the metal is being dissolved, hydrogen is being formed at the metal surface at the same time. Being the smallest chemical element, hydrogen can easily diffuse into the metal lattice. There, is reacts to the metal hydride and may even form bubbles. By the phase change it creates pressure. The hydride is very brittle, and the metal can easily fail mechanically. In order to prevent catastrophic hydrogen embrittlement, small amounts of platinum were implanted into the surface of metallic tantalum and of tantalum coated with a protective oxide film. Depth profiles by secondary ion mass spectrometry showed that the platinum was located close to the surface; the implantation zone of the oxidized tantalum was considerably thicker than the one of the bare tantalum. Upon exposure to hot mineral acids, the untreated tantalum failed in mechanical tests due to embrittlement after short time, while the platinum-implanted one achieved considerably enhanced life-times. No difference was found between the bare and the oxide-coated tantalum.

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