Effect of Inclusion Size and Distribution on the Corrosion Behavior of Medical-Device Grade Nitinol Tubing

Wohlschlögel, M.; Steegmüller, R.; Schüßler, A.

doi:10.1007/s11665-014-0996-6

Cited by 29 publications

(26 citation statements)

References 6 publications

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“…The results obtained in this study and by Tuissi et al together with the work by Wohlschlogel et al indicate that inclusion size is a key factor, irrespective of the type of inclusion. Wohlschlogel et al found that breakdown did occur on some test samples in which the mean diameter of the inclusions was about 3 µm.…”

Section: Discussionsupporting

confidence: 76%

“…Wohlschlögel et al considered voids around inclusions in EP nitinol to be the likely cause of pitting, based on their findings that inclusion diameter correlated with the percentage of breakdowns in potentiodynamic polarization tests . They reasoned that a larger inclusion is typically associated with a larger void and therefore a higher probability that the void will intersect the surface as a crevice to promote localized corrosion.…”

Section: Discussionmentioning

confidence: 99%

“…Several studies have shown that inclusion size is a key factor in pitting of nitinol . Wohlschlögel et al indicated that the percentage of breakdowns in cyclic polarization tests with EP nitinol vascular implants increases with mean inclusion diameter above ∼8 µm; that is, a larger inclusion diameter generally leads to a higher percentage of breakdowns .…”

Section: Introductionmentioning

confidence: 99%

“…Wohlschlögel et al indicated that the percentage of breakdowns in cyclic polarization tests with EP nitinol vascular implants increases with mean inclusion diameter above ∼8 µm; that is, a larger inclusion diameter generally leads to a higher percentage of breakdowns . Further work by Wohlschlögel et al showed that the susceptibility of EP nitinol to pitting corrosion was affected by inclusion size rather than inclusion quantity . No distinction was made between the types of inclusions in either of these studies, but other work has shown that the breakdown potential of MP (diamond paste) nitinol is decreased by the presence of large TiC particles …”

Section: Introductionmentioning

confidence: 99%

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Pit initiation on nitinol in simulated physiological solutions

Pound

2017

J Biomed Mater Res

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Inclusions appear to play a crucial role in the initiation of pitting on nitinol, but the reason remains unclear. Furthermore, it has not been established whether the type of inclusion is a central factor. In this study, potentiodynamic polarization together with scanning electron microscopy and energy dispersive X-ray spectroscopy were used to provide more insight into the initiation of pits on electropolished nitinol wire. Corrosion was limited to a single primary pit on each of the few wire samples that exhibited breakdown. The pit contained numerous Ti NiO inclusions, but secondary pits that developed within the primary pit provided evidence that these inclusions were the sites of pit initiation. Although several theories have been proposed to account for pit initiation at inclusions in mechanically polished and electropolished nitinol, titanium depletion in the adjacent alloy matrix appears to provide the most viable explanation. The key factor appears to be the size of the inclusion and therefore the extent of titanium depletion in the alloy matrix. The type of inclusion evidently plays a secondary role at most. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1605-1610, 2018.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pit initiation on nitinol in simulated physiological solutions

Pound

2017

J Biomed Mater Res

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“…During each tube drawing step, inclusions are further fractionalized and the inclusion size decreases. Since the fraction of breakdowns correlates rather with inclusion size than with inclusion quantity, the resistance against localized corrosion improves with increasing number of tube drawing step [27]. Sputtered NiTi thin films reveal, in this respect, exciting results due to their complete lack of carbide or oxide inclusions.…”

Section: Introductionmentioning

confidence: 99%

Method for Fabricating Miniaturized NiTi Self-Expandable Thin Film Devices with Increased Radiopacity

Bechtold¹,

Miranda²,

Chluba

et al. 2016

Shap. Mem. Superelasticity

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Nitinol is the material of choice for many medical applications, in particular for minimally invasive implants due to its superelasticity and biocompatibility. However, NiTi has limited radiopacity which complicates positioning in the body. A common strategy to increase the radiopacity of NiTi devices is the addition of radiopaque markers by micro-riveting or micro-welding. The recent trend of miniaturizing medical devices, however, reduces their radiopacity further, and makes the addition of radiopaque markers to these miniaturized devices difficult. NiTi thin film technology has great potential to overcome such limitations and to fabricate new generations of miniaturized, self-expandable NiTi medical devices with additional functionalities, such as structured multilayer devices with increased radiopacity. For this purpose, we have produced superelastic thin film NiTi samples covered locally with Tantalum structures of different thickness and different shape. These multilayer devices were characterized regarding their mechanical and corrosion properties as well as their X-ray visibility. The superelastic behavior of the underlying NiTi layer is impeded by the Ta layer, and shows therefore a dependence on the Tantalum patterning geometry and thickness. No delamination was observed after mechanical and corrosion tests. The multilayers reveal excellent corrosion resistance, as well as a significant increase in radiopacity.

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Nitinol: Tubing versus sputtered film – microcleanliness and corrosion behavior

et al. 2015

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Corrosion behavior and microcleanliness of medical-device grade Nitinol tubing (Nix Ti1- x , x = 0.51; outer diameter 7 mm, wall thickness 0.5 mm), drawn from various ingot qualities, are compared to the characteristics of sputtered Nitinol film material (Nix Ti1- x , x = 0.51; thickness 50 µm). Electropolished tubing half-shell samples are tested versus as-received sputtered film samples. Inclusion size distributions are assessed using quantitative metallography and corrosion behavior is investigated by potentiodynamic polarization testing in phosphate-buffered saline at body temperature. For the sputtered film samples, the surface chemistry is additionally analyzed employing Auger Electron Spectroscopy (AES) composition-depth profiling. Results show that the fraction of breakdowns in the potentiodynamic polarization test correlates with number and size of the inclusions in the material. For the sputtered Nitinol film material no inclusions were detectable by light microscopy on the one hand and no breakdowns were found in the potentiodynamic polarization test on the other hand. As for electropolished Nitinol, the sputtered Nitinol film material reveals Nickel depletion and an Oxygen-to-Titanium intensity ratio of ∼2:1 in the surface oxide layer, as measured by AES. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1176-1181, 2016.

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Effect of Inclusion Size and Distribution on the Corrosion Behavior of Medical-Device Grade Nitinol Tubing

Cited by 29 publications

References 6 publications

Pit initiation on nitinol in simulated physiological solutions

Pit initiation on nitinol in simulated physiological solutions

Method for Fabricating Miniaturized NiTi Self-Expandable Thin Film Devices with Increased Radiopacity

Nitinol: Tubing versus sputtered film – microcleanliness and corrosion behavior

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