Strategies to improve the corrosion resistance of microarc oxidation (MAO) coated magnesium alloys for degradable implants: Prospects and challenges

Narayanan, T.S.N. Sankara; Park, Il Song; Lee, Min Ho

doi:10.1016/j.pmatsci.2013.08.002

Cited by 546 publications

(183 citation statements)

References 285 publications

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“…Fortunately, research from the past 40 years has made tremendous progress in exploring the PEO fundamentals, largely due to the efforts of European and Russian researchers. These achievements have been summarized in several reviews [4,[26][27][28][29][30]. It is worth mentioning that plasma electrolytic oxidation belongs to a branch of electrolytic plasma technology, including many surface treatments with the metal sample as a cathode or anode surrounded by a gas envelope accompanied by luminous discharges.…”

Section: Introductionmentioning

confidence: 99%

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Tsai

Chou

2018

Metals

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Abstract:A dense inner layer is highly valued among the surface coatings created through plasma electrolytic oxidation (PEO) treatment, because the PEO coating has been troubled by inherent porosity since its conception. To produce the favored structure, a proven technique is to prompt a soft sparking transition, which involves a sudden decrease in light and acoustic emissions, and a drop in anodic voltage under controlled current mode. Typically these phenomena occur in an electrolyte of sodium silicate and potassium hydroxide, when an Al-based sample is oxidized with an AC or DC (alternating or direct current) pulse current preset with the cathodic current exceeding the anodic counterpart. The dense inner layer feature is pronounced if a sufficient amount of oxide has been amassed on the surface before the transition begins. Tremendous efforts have been devoted to understand soft sparking at the metal-oxide-electrolyte interface. Studies on aluminum alloys reveal that the dense inner layer requires plasma softening to avoid discharge damages while maintaining a sufficient growth rate, a porous top layer to retain heat for sintering the amassed oxide, and proper timing to initiate the transition and end the surface processing after transition. Despite our understanding, efforts to replicate this structural feature in Mg-and Ti-based alloys have not been very successful. The soft sparking phenomena can be reproduced, but the acquired structures are inferior to those on aluminum alloys. An analogous quality of the dense inner layer is only achieved on Mg-and Ti-based alloys with aluminate anion in the electrolytic solution and a suitable cathodic current. These facts point out that the current soft sparking knowledge on Mg-and Ti-based alloys is insufficient. The superior inner layer on the two alloys still relies on rectification and densification of aluminum oxide.

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Section: Introductionmentioning

confidence: 99%

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Tsai

Chou

2018

Metals

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“…Clearly, controlling the corrosion rate is required to make use of magnesium and its alloy materials feasible for surgical implantation. Lots of methods have been introduced to hinder corrosion rate of magnesium-based materials by surface modification methods including plasma anodization [23], microarc oxidation [24], as well as polymer coating [25,26]. Among them, polymer coating not only is potential to corrosion resistance, but also can act as a drug reservoir [3,27,28].…”

Section: Surface Modification Strategiesmentioning

confidence: 99%

The Surface Modification Methods for Constructing Polymer-Coated Stents

Fan

Yang

2018

International Journal of Polymer Science

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Implanting a metal stent plays a key role in treating cardiovascular diseases. However, the high corrosion rate of metal-based devices severely limits their practical applications. Therefore, how to control the corrosion rate is vital to take full advantages of metal-based materials in the treatment of cardiovascular diseases. This review details various methods to design and construct polymer-coated stents. The techniques are described and discussed including plasma deposition, electrospinning, dip coating, layer-by-layer self-assembly, and direct-write inkjet. Key point is provided to highlight current methods and recent advances in hindering corrosion rate and improving biocompatibility of stents, which greatly drives the rising of some promising techniques involved in the ongoing challenges and potential new trends of polymer-coated stents.

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“…Although the fluoride was found to be beneficial for the osteointegration in the early stage of bone tissue healing [32], the controversies about fluorosis caused by excess fluoride still exist [33]. As the thickness, structure, and phase composition of the PEO coating can be adjusted by the process parameters [34], the fabrication of the MgO and MgF 2 containing coating by PEO method is applicable to control the contents of MgF 2 phase, obtaining stable coating structure as well as better biological responses. After hydrothermal treatment, the feature peaks of Mg, MgO, MgF 2 and hydroxyapatite (HA) (JCPDS #09-0432) were all detected in the pattern of PEO/HT.…”

Section: Coatings Characterizationmentioning

confidence: 99%