Countermeasure for corrosion and hydrogen embrittlement of Ni-Ti superelastic alloy in acidic fluoride solution by adding sodium bicarbonate and hydrogen peroxide

ABSTRACT

Development of countermeasure for corrosion and hydrogen embrittlement of Ni-Ti superelastic alloy in an acidulated phosphate fluoride (APF) solution has been attempted by adding NaHCO₃ and H₂O₂ to the solution. Upon addition of only 0.001 M NaHCO₃ to a 0.2% APF solution, almost no changes in corrosion current density and corrosion potential are observed. With an increasing NaHCO₃ concentration up to 0.01 M, the corrosion current density substantially decreases and the corrosion potential slightly shifts in the noble direction. The corrosion loss significantly decreases and hydrogen absorption is slightly inhibited. Upon the combined addition of 0.01 M NaHCO₃ and 0.001 M H₂O₂, the corrosion current density is lowest and the corrosion potential shifts in the noble direction. The corrosion and hydrogen absorption are substantially inhibited. The present study clearly indicates that the combined addition is exceptionally effective as a simultaneous countermeasure for corrosion and hydrogen embrittlement of the alloy.

KEYWORDS:

• Nitinol
• shape memory alloy
• biomaterials
• corrosion
• hydrogen embrittlement
• fluoride
• sodium hydrogen carbonate

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by JSPS KAKENHI [Grant Number 15K06507].