In situ quantification of electrochemical dissolution of hafnium-tantalum alloys in acidic media

•Hf–Ta alloys electrochemical dissolution was studied in a wide compositional range.•A flow-type scanning droplet cell microscope was used for acidic media dissolution.•Downstream analytics were used for the quantification of Hf and Ta amounts dissolved.•Hf and Ta dissolution rates were in the ng and pg s− 1 cm− 2 range, respectively.•A dissolution enhancement of minor species was identified in Hf–Ta alloys.

A thin film hafnium-tantalum combinatorial library with a compositional spread of over 70 at.% was used for electrochemical dissolution experiments in nitric acid. Surface microstructure analysis and crystallographic characterization of individual Hf–Ta alloys confirmed a hexagonal to tetragonal transition from pure Hf to pure Ta accompanied by a change in the surface grain structure. A flow-type scanning droplet cell microscope coupled to downstream analytics was used for the quantification of Hf and Ta dissolution rates along the entire compositional spread. Potentiostatically applying 3 V vs. SHE for 120 s for an electrolyte flow of 0.46 ml min− 1 resulted in dissolution rates of pure Hf and pure Ta in the ng s− 1 cm− 2 and pg s− 1 cm− 2 range, respectively. For both species, the average dissolution rate was independent of the compositional gradient, indicating a dissolution enhancement of minor species. A decrease in their activation energy for dissolution triggered by a surface energy modification was the reason for the observed behavior.

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