Effects of strontium-substitution in sputter deposited calcium phosphate coatings on the rate of corrosion of magnesium alloys

Jonathan G. Acheson, Stephen McKillop, Joanna Ward, Abhijit Roy, Zhigang Xu, Adrian R. Boyd, Patrick Lemoine, Prashant N. Kumta, Jagannathan Sankar, Brian J. Meenan

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Abstract

Magnesium (Mg) alloys have significant potential for use as bioresorbable orthopaedic implant devices due to their controllable mechanical properties and an ability to promote new bone growth. However, difficulty lies with controlling the rate of corrosion in physiological conditions to ensure the load-bearing capability of the device is maintained for the required period of time, specifically until an adequate quantity of new bone tissue is formed. In this work, RF magnetron sputtering has been used to create calcium phosphate (CaP) and strontium-substituted calcium phosphate (SrCaP) thin film coatings on two Mg alloy systems (denoted WJK and ZEWX) that have been formulated for the fabrication of orthopaedic fracture fixation devices. A 14-day static-dynamic immersion study in simulated body fluid (SBF), shows that uncoated WJK substrates had a corrosion rate of 4.04 ± 0.15 millimetres per year (mmpy), which was reduced to 3.22 ± 0.17 mmpy with the application of a CaP coating, and to 2.92 ± 0.05 mmpy with a SrCaP coating. Uncoated ZEWX substrates had a corrosion rate of 3.36 ± 0.05 mmpy which was reduced to 2.98 ± 0.19 mmpy and 2.79 ± 0.03 mmpy, for CaP and SrCaP coatings, respectively. Whereas the sputter-deposited CaP and SrCaP coatings completely dissolve in SBF over the period of immersion, their presence at the outset significantly decreases the corrosion rate of both Mg alloys, as compared to the values for the uncoated substrates. Successful incorporation of Sr within the coating offers the potential for improved bioactivity with respect to directing the bone cell response to create new tissue.
Original languageEnglish
Article number127446
JournalSurface and Coatings Technology
Volume421
Early online date24 Jun 2021
DOIs
Publication statusPublished - 15 Sep 2021

Bibliographical note

Funding Information:
Ulster University acknowledges funding from the Department for the Economy (DfE), Northern Ireland (Grant USI 111 ). University of Pittsburgh and North Carolina Agricultural and Technical State University acknowledge funding and the support via the National Science Foundation (NSF) funded Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB) (Grant EEC-0812348 ).

Funding Information:
The authors wish to acknowledge support for this work from a US-Ireland Centre-to-Centre R&D Partnership between Ulster University , North Carolina Agricultural and Technical State University , University of Pittsburgh , University of Cincinnati , Cincinnati Children's Hospital , and the National University of Ireland Galway . P.N.K. would also like to acknowledge the financial support from the Edward R. Weidlein Endowed Chair Professorship Funds , and the Center for Complex Engineered Multifunctional Materials (CCEMM) at the Swanson School of Engineering in the University of Pittsburgh for use of the equipment and instrumentation needed for preparing the alloys described herein.

Publisher Copyright:
© 2021 The Author(s)

Keywords

  • Corrosion rate
  • Magnesium alloys
  • Micro-computed tomography (μCT)
  • RF magnetron sputter deposition
  • Strontium-substituted calcium phosphate coatings

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