posted on 2023-11-30, 07:20authored byXian-Ze Meng, Xin-Ran Li, Fei Li, Hao-Jie Yan, Qin-Hao Zhang, Lian-Kui Wu, Devis Di Tommaso, Fa-He Cao
Titanium
and its alloys are protected by a compact and stable passive
film, which confers resistance to corrosion by the primary halogen
chloride (Cl–) while being less effective against
fluoride (F–). Although researchers have recognized
different macroscopic corrosion effects of these halide ions on titanium,
the underlying mechanisms remain largely unexplored. In this work,
the bonding of Cl–/F– with stable
passive films was studied in neutral and acidic (pH = 2.3) conditions.
The synergistic effect between the interfacial hydrogen bond (HB)
structure and halogens on titanium corrosion was first revealed using
first-principles calculation and Raman spectroscopy. F– forms more stable halogen–Ti bonds than Cl–, resulting in titanium degradation. The proton combined with F– exhibits a specific synergistic effect, causing corrosion
of the passive film. The water hydrogen bond transformation index
(HBTI) at the titanium/aqueous interface was 1.88 in an acidic solution
containing F–, significantly higher than that in
neutral/acid solutions containing Cl– (1.80/1.81)
and a neutral solution containing F– (1.81). This
work clarifies the structure–activity relationship between
HBTI and the destruction of titanium passive films. We propose that
the microstructure of the interfacial HB is an undeniable factor in
the corrosion of titanium.