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Abstract: Mechanical and chemical durability is of equal importance as bio-functionality for surface-modifying films on biomedical devices. This is in particular true for those serving on combined conditions of loading and a corrosive ambient. In this work, we investigated the deformation and corrosion behaviors of Ti–O films coated onto 316L stainless steel aimed for cardiovascular stent applications. The Ti–O films were synthesized by plasma immersion ion implantation and deposition (PIII&D), and the investigation conditions were as required for cardiovascular stents concerning plastic deformation and corrosion. Tensile and three point bending tests showed that no peeling and delaminating occurred on the Ti–O film which had undergone relatively high plastic deformation (4% to16% elongation). Electrochemical corrosion tests showed that the deformed PIII&D Ti–O film coated 316L SS suffered more severe corrosion in simulated body fluid (SBF) than the non-deformed, but remained comparable to uncoated 316L SS, which is clinically acceptable for stents. Due to the good mechanical and chemical durability as well as biomedical functionalities, the PIII&D Ti–O films appear promising as surface-modification of cardiovascular stents in real applications. [Copyright &y& Elsevier]

An in-situ and real-time electrochemical study in a vascular bioreactor was designed to analyze corrosion mechanism of magnesium alloy (MgZnCa) under mimetic hydrodynamic conditions. Effect of hydrodynamics on corrosion kinetics, types, rates and products was analyzed. Flow-induced shear stress (FISS) accelerated mass and electron transfer, leading to an increase in uniform and localized corrosions. FISS increased the thickness of uniform corrosion layer, but filiform corrosion decreased this layer resistance at high FISS conditions. FISS also increased the removal rate of localized corrosion products. Impedance-estimated and linear polarization-measured polarization resistances provided a consistent correlation to corrosion rate calculated by computed tomography. [ABSTRACT FROM AUTHOR]

Abstract: Ti–O film was deposited on cobalt-chromium alloy (L-605) coronary stents by metal vacuum arc source deposition. The corrosion resistance of the Ti–O film modified and bare L-605 stents was investigated by cyclic potentiodynamic polarization tests in phosphate buffered solution (PBS, 37±1°C). The optical microscopy and scanning electron microscopy (SEM) images of the modified stents indicated that the surface of all stent cells was very smooth and uniform, and the thickness of Ti–O film was about 10nm. There were not any cracks and delamination on stent surface after dilation by angioplasty. The polarization results showed that the natural corrosion potential of the Ti–O film modified and bare stents was similar. But the corrosion current density of Ti–O film modified stent was lower than that of the bare stent at all scanned potential range. Compared with Ti–O film modified stent, the bare stent was more susceptible to corrosion. After cyclic potentiodynamic polarization test, the slight localized corrosion was found on the surface of bare stents. But no film flakes or localized pitting can be observed on Ti–O film modified stent. All these results showed that Ti–O film modified stent had the better corrosion resistance, compared with the bare L605 stent. [Copyright &y& Elsevier]

Graphical abstract Highlights • The negative difference effect of Mg is fathomed in a revisited view. • The exposed area of Mg is enlarged under galvanostatic anodic polarization. • The anodic hydrogen is associated with exposed fresh Mg. • The anodic hydrogen is mainly released by chemical reaction between Mg and water. Abstract The driving force of hydrogen evolution (HE) on Mg anode was investigated by continuously enlarging the exposed area of fresh Mg via mechanical rubbing and chemical attack during anodic polarization. The data show that release of hydrogen on Mg anode was mainly associated with exposed Mg. Meanwhile, the differences in anodic HE behaviors obtained with two exposure methods indicate that hydrogen was predominantly generated via chemical reaction between Mg and electrolyte on Mg anode surface. [ABSTRACT FROM AUTHOR]

To address insufficient corrosion control of polymer-coated magnesium, we apply a hydrophobic stearic acid (SA) thin layer underlying the poly (lactic acid) (PLA) and poly (ε-caprolactone) (PCL) coatings on Mg. The SA imbedded polymer-coated Mg showed apparently smaller corrosion current density than the direct-coated counterparts. More importantly, they exhibited manifestly slower and more stable long-term in vitro immersion degradation than the direct polymer-coated Mg up to 21 days. Moreover, the scratch testing disclosed their undercutting corrosion was suppressed evidently. The strengthened corrosion control by the imbedded layer is attributed to its kinetic barrier, hydrophobic nature as well as shielding effect. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Zn was compared with those of Fe and Mg in a long-term course of immersing in phosphate buffered saline (PBS) as biodegradable metal for bio-implants application. The comparison focused on corrosion rate, mode, products and surface characteristics along the immersion degradation up to 21 days. For transient assays, the open circuit potential and corrosion rate placed Zn between Fe and Mg. However, in a long-term course the corrosion rate of Zinc developed faster than Fe and Mg. This was ascribed to its unique localized corrosion and corrosion products changing in contrast to Fe and Mg. [ABSTRACT FROM AUTHOR]

A polydopamine (PDA) layer was sandwiched between a TiO 2 coating and Mg substrate to enhance the corrosion protection. The PDA layer was covalently immobilized on Mg, and the TiO 2 was coated by liquid phase deposition subsequently on it. The hybrid TiO 2 /PDA coated Mg exhibited significantly smaller free corrosion current density as well as a remarkably lower degradation rate in vitro (up to 21 days) in phosphate buffered saline compared to direct TiO 2 coated and untreated Mg. The efficacy is ascribed to the organic PDA layer which suppresses the electric pathway of galvanic corrosion cell and therefore corrosion rate of magnesium. [ABSTRACT FROM AUTHOR]

A protective chemical conversion coating based on epigallocatechin gallate (EGCG) was developed on MgZnMn alloy, where the formation of EGCG–metal complexes protected the corrosion of metal substrate from its environment. The coating was prepared via one-step immersion in the EGCG solution. The morphology, formation mechanism and corrosion resistance of the coating were found to be EGCG-concentration dependent. The EGCG conversion coating modified the MgZnMn showed substantially higher corrosion resistance as compared to bare MgZnMn according to the immersion and electrochemical tests. The present study suggests that the EGCG-coated MgZnMn alloy has a high potential for the application as implants due to the facility and effectiveness of the application. [ABSTRACT FROM AUTHOR]

The polymerized Hydroxyquinoline (HQ) coatings incorporated with corrosion inhibitor nano-Graphene Oxide (GO) particles were fabricated on treated magnesium AZ31 alloy. The effect of surface treatment of AZ31 using either oxidation or phosphating was much more effective than GO embedment on the corrosion resistance and self-healing functionality. Surface treatment prior to GO/HQ deposition plays a vital role in initiating more anchoring bonds between molecules to fasten any scratch healing. The anticorrosion behavior of the GO/HQ hybrid coating will be discussed in the light of SEM, XRD, XPS and FTIR analysis. Unlabelled Image • Embedment of self-healing GO particles into HQ films upon AZ31had been demonstrated • HQ-GO/MgO/AZ31 film presented self-healing functionality plus anti-corrosion ability • AZ31 oxidation initiated anchoring bonds between GO and Mg to fasten scratch healing. • Carbonyl group (C O) and honeycomb-structure morphology are master keys for protection. [ABSTRACT FROM AUTHOR]