Inhibition of hydrogen embrittlement of Ni–Ti superelastic alloy in acid fluoride solution by hydrogen peroxide addition

Abstract

Inhibition of the hydrogen embrittlement of Ni-Ti superelastic alloy in an acidulated phosphate fluoride (APF) solution has been attempted by adding various amounts of H(2)O(2). In a 0.2% APF solution, hydrogen absorption is markedly inhibited by adding H(2)O(2), although corrosion is slightly enhanced by increasing the amount of added H(2)O(2). By adding a small amount of H(2)O(2) (0.001 M), in the early stage of immersion, hydrogen embrittlement is inhibited and corrosion is only slightly enhanced. Upon adding H(2)O(2), it appears that the dominant cathodic reactions change from hydrogen evolution to H(2)O(2) reduction reactions, or the surface conditions of the alloy are changed by H(2)O(2) with a high oxidation capability, thereby inhibiting hydrogen absorption. The present study clearly indicates that infinitesimal addition of H(2)O(2) into acid fluoride solutions is effective for the inhibition of the hydrogen embrittlement of the alloy.

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

“…With increasing H 2 O 2 concentration up to 0.01 M in the solution with 0.001 M or 0.01 M NaHCO 3 , the corrosion current density (0.76 ± 0.22 A/m 2 or 0.57 ± 0.17 A/m 2 ) increased near that in the 0.2% APF solution without addition (0.74 ± 0.09 A/m 2 ). As reported previously [26], the increase in H 2 O 2 concentration probably enhances corrosion even in the 0.2% APF solution with NaHCO 3 . The corrosion potential shifted in the noble direction of approximately 0.15-0.2 V with increasing H 2 O 2 concentration.…”

“…Upon adding H 2 O 2 in the solutions with NaHCO 3 , as shown in Figure 2(b), the corrosion potential shifted in the noble direction with increasing H 2 O 2 concentration (around −0.3 V vs. SCE) and then became stable. The shift is probably associated with the marked growth of the oxide film attributable to H 2 O 2 with high oxidation capability [26,33,34].…”

“…However, surface modifications such as coating are not always suitable because coating layers break during superelastic deformation [22][23][24][25] and elaborate surface modifications increase the cost of orthodontic wires. On the other hand, as a countermeasure for hydrogen embrittlement, we have proposed the addition of an infinitesimal quantity of hydrogen peroxide (H 2 O 2 ), which has high oxidation capability, to 0.2% acidulated phosphate fluoride (APF) aqueous solution [26]. In this case, although the corrosion current density slightly increases upon addition of H 2 O 2 at higher than 0.01 M, as shown in the potentiodynamic polarisation curve, the corrosion potential shifts in the noble direction and dominant cathodic reactions change from hydrogen evolution to H 2 O 2 reduction reactions [26].…”

Corrosion performance of medical grade NiTi after laser processing

“…This may be because the post-process etching time was significantly shorter in duration than the original etching treatment. This shorter etching time was used to avoid over etching the retained original CE surfaces, which could lead to hydrogen embrittlement [32]. A slight increase in the oxide peak observed by Raman spectroscopy (see Figure 6) reveals that is was a valid concern, because increasing the crystallinity of Ti can lead to brittleness [33].…”

The effect of simulating porcelain firing on the elemental composition, microstructure, and mechanical properties of electroformed gold restorations

“…In addition, previous studies have reported that electroformed structures contain light elements such as C, O, and N, which are retained in their structure, probably during the manufacturing process 10 . These low-atomic-number elements with small atomic radii can be dissolved in a metallic structure, forming an interstitial solid solution with increased hardness and tensile strength at the expense of ductility and fracture strength, as in the case of hydrogen embrittlement 16 . In addition, they might be implicated in further changes in mechanical properties during porcelain firing, because the firing temperature (780°C) is very close to the melting point of pure Au (1064°C), and various mechanisms might be triggered.…”