Deep inside of the mechanism of electrochemical surface etching of α + β Ti6Al4V alloy in room-temperature deep eutectic solvent Ethaline

A deep eutectic solvent Ethaline, composing of choline chloride (vitamin B 4) and ethylene glycol, is presented as electrochemical surface modification agent for Ti6Al4V alloy. The possibility of creation of highly rough topography with cell-sized micropits for successful bioinspiration by electrochemical etching is demonstrated and probed in depth. STEM-EDS investigation is clarifying the dissolution process of α and β-Ti phases in the alloy and the formation of amorphous nano-sized TiOx tubular units as the dissolution products. EELS plasmon mapping and MLLS fitting is used to attest the absence of hydrides that could lead to severe material degradation. Outermost layer, which consists mainly of Cl and O with a thickness of ∼ 50 nm, is detected only after electrochemical etching of Ti6Al4V alloy in Ethaline.