Corrosion of porous Mg and Fe scaffolds: a review of mechanical and biocompatibility responses

Abstract

Absorbable metals have been proposed as potential materials for hard tissue scaffolding to offer both high mechanical support and bioabsorbability. Over the past 5 years, many works sought evidence of the interesting mechanical property which mimics to that of human bone with tailored corrosion behaviour. The emerging additive manufacturing (AM) technology helps to optimise the design and production of topological porous absorbable metals suited for bone scaffolds. Since the studies on the porous absorbable metals are on the rise, we provide a current state-of-the-art of corrosion performances for porous Mg-based and Fe-based scaffolds including recent developments and the remaining challenges. A detailed discussion on the impacts of advanced AM and recently developed dynamic-flow corrosion on their in vitro corrosion, mechanical strengths and biocompatibility are also provided. This review also analyses the suitability of both metals to be used for bone substitute materials.

Insight into the bioabsorption of Fe‐based materials and their current developments in bone applications

“…[30] Another important factor affecting the corrosion behavior of Fe is the formation of corrosion products on its surface. [31] The Fe ions will react with OH − to produce Fe(OH) 2 according to reaction (3). The ferrous oxides can further oxidize to ferric oxides as stated in Equation (4).…”

“…[34] The dense and strongly adhered oxides or hydroxides of Fe with a very low aqueous solubility formed on Fe surface are one of the factors contributing to this slow corrosion rate. [31] Fe 2+ and Fe 3+ make up the formation of common Fe(OH) 2 , Fe 2 O 3 , Fe 3 O 4 , Fe(OH) 3 , [35,36] and other corrosion products species such as α-FeOOH, FeCO 3 , and (MgFe) 3 (PO4) 2 .8H 2 O. [30,35,37] FeOOH products.…”

Modifications on porous absorbable Fe‐based scaffolds for bone applications: A review from corrosion and biocompatibility viewpoints

“…The corrosion rate of Fe in physiological environments is considered excessively slow for bioresorbable applications 4 . The continuous formation of poorly soluble corrosion products on its surface over corrosion period is one of the factors contributing to its low corrosion kinetics 24 . The lower solubility of these corrosion products which could act as a dense protective layer hinder O 2 diffusion to the Fe surface and thus decelerating the redox reactions.…”

Microstructure, Mechanical, In Vitro Biodegradation, and Antimicrobial Behavior of a Mg-Zn-Ca-Sr/ZrO2 Composite Prepared Using Powder Metallurgy

“…12 Powder metallurgy as a processing technique is a reasonably useful route to prepare alloys to improve mechanical and corrosive properties as its fabrication in the porous form may also be an essential feature of biodegradable implants during degradation. 14,15 The present research is a modest attempt to reach the essential properties of a biodegradable Mg alloy for an ideal biodegradable implant for orthopedic application, where a…”

“…The balance between the two is still under unacceptable limits as previously described based on the bone-biodegradable implant interface, which primarily depended on the materials to be used for biodegradable implants. ,− Mg alloy/composites with nutrients and other useful biocompatible elements, such as Ca, Zn, Sr, zirconia (ZrO 2 ), hydroxyapatite (HA), and so forth, can be an excellent step for adequacy of all such performance of biodegradable implant, not only to improve mechanical and biodegradation performance but also to improve bone healing. ,, ZrO 2 is a biocompatible and nontoxic element that can be used as an improvement in mechanical performance in all. − As a possibility with a suitable combination, a multiphase metal matrix with ceramic composites could provide all the properties needed in an ideal biodegradable bone implant . Powder metallurgy as a processing technique is a reasonably useful route to prepare alloys to improve mechanical and corrosive properties as its fabrication in the porous form may also be an essential feature of biodegradable implants during degradation. , …”