Lan-Yue Cui

Corrosion Resistance of Superhydrophobic Mg-Al Layered Double Hydroxide Coatings on Aluminum Alloys

AbstractA superhydrophobic surface was successfully constructed to modify the layered double hydroxide (LDH) coatings on aluminum alloy using stearic acid. The characteristics of the coatings were investigated using SEM, XRD, FT-IR and XPS. The corrosion resistance of the prepared coatings was studied using potentiodynamic polarization and electrochemical impedance spectrum. The results revealed that the superhydrophobic surface considerably improved the corrosion-resistant performance of the LDH coatings on the aluminum alloy substrate. The formation mechanism of the superhydrophobic surface was proposed.

Corrosion resistance of layer-by-layer assembled polyvinylpyrrolidone/polyacrylic acid and amorphous silica films on AZ31 magnesium alloys

A layer-by-layer (LbL)-assembled composite coating containing SiO2 and a biocompatible polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) multi-layer, designated as SiO2/(PVP/PAA)5, was prepared on AZ31 Mg alloy via dip-coating. The surface morphology, microstructure and chemical composition of the coating were investigated using FE-SEM, FT-IR, XRD and XPS. The physical properties of the coating were characterized by scratch testing. The results demonstrated that the coating was amorphous and remarkably soft. PVP and PAA promoted the formation of Ca–P precipitates, and the amorphous silica film further enhanced corrosion resistance. The SiO2/(PVP/PAA)5 coating may be a promising surface modification for degradable Mg cardiovascular stents.

Corrosion resistance of biodegradable polymeric layer-by-layer coatings on magnesium alloy AZ31

Biocompatible polyelectrolyte multilayers (PEMs) and polysiloxane hybrid coatings were prepared to improve the corrosion resistance of biodegradable Mg alloy AZ31. The PEMs, which contained alternating poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH), were first self-assembled on the surface of the AZ31 alloy substrate via electrostatic interactions, designated as (PAH/PSS)5/AZ31. Then, the (PAH/PSS)5/AZ31 samples were dipped into a methyltrimethoxysilane (MTMS) solution to fabricate the PMTMS films, designated as PMTMS/(PAH/PSS)5/AZ31. The surface morphologies, microstructures and chemical compositions of the films were investigated by FE-SEM, FTIR, XRD and XPS. Potentiodynamic polarization, electrochemical impedance spectroscopy and hydrogen evolution measurements demonstrated that the PMTMS/(PAH/PSS)5/AZ31 composite film significantly enhanced the corrosion resistance of the AZ31 alloy in Hank’s balanced salt solution (HBSS). The PAH and PSS films effectively improved the deposition of Ca-P compounds including Ca3(PO4)2 and hydroxyapatite (HA). Moreover, the corrosion mechanism of the composite coating was discussed. These coatings could be an alternative candidate coating for biodegradable Mg alloys.

In vitro corrosion resistance and antibacterial properties of layer-by-layer assembled chitosan/poly-L-glutamic acid coating on AZ31 magnesium alloys

Abstract Surface functionalization of magnesium (Mg) alloys is desired to obtain the surfaces with both improved corrosion resistance and antibacterial property. A corrosion-resistant and antimicrobial coating was prepared on Mg alloy surface by layer-by-layer (LbL) assembly of chitosan (CHI) and poly-L-glutamic acid (PGA) by electrostatic attraction. The functionalized surfaces of the Mg alloys were characterized by field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and electrochemical tests. The bactericidal activity of the samples against Staphylococcus aureus was assessed by the zone of plate-counting method. The obtained coating on the Mg alloy substrates exhibits good corrosion resistance and antibacterial performance.

Corrosion Resistance of Silane-Modified Hydroxyapatite Films on Degradable Magnesium Alloys

A polymethyltrimethoxysilane (PMTMS)/hydroxyapatite (HA) hybrid coating was successfully fabricated on a magnesium alloy by hydrothermal treatment and immersion method. The microstructure and composition of the coating were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The physical properties were investigated using scratch testing. At the same time, the corrosion resistance was evaluated via electrochemical and immersion tests. The results demonstrated that the corrosion resistance of the silane hybrid coating was significantly enhanced compared with the naked magnesium alloy. Especially, the corrosion current density of the PMTMS/HA magnesium alloy was three orders of magnitude lower than that of the bare material.

In Vitro Degradation of Pure Magnesium―The Effects of Glucose and/or Amino Acid

The influences of glucose and amino acid (L-cysteine) on the degradation of pure magnesium have been investigated using SEM, XRD, Fourier transformed infrared (FTIR), X-ray photoelectron spectroscopy (XPS), polarization and electrochemical impedance spectroscopy and immersion tests. The results demonstrate that both amino acid and glucose inhibit the corrosion of pure magnesium in saline solution, whereas the presence of both amino acid and glucose accelerates the corrosion rate of pure magnesium. This may be due to the formation of -C=N- bonding (a functional group of Schiff bases) between amino acid and glucose, which restricts the formation of the protective Mg(OH)2 precipitates.

In vitro corrosion of Mg--Ca alloy --- The influence of glucose content

Influence of glucose on corrosion of biomedical Mg-1.35Ca alloy was made using hydrogen evolution, pH and electrochemical polarization in isotonic saline solution. The corrosion morphologies, compositions and structures were probed by virtue of SEM, EDS, FTIR, XRD and XPS. Results indicate that the glucose accelerated the corrosion of the alloy. The elemental Ca has no visible effect on the corrosion mechanism of glucose for the Mg-1.35Ca alloy in comparison with pure Mg. In addition, the presence of CO2 has beneficial effect against corrosion due to the formation of a layer of carbonatecontaining products.

Corrosion resistance of a novel SnO2-doped dicalcium phosphate coating on AZ31 magnesium alloy

A SnO2-doped dicalcium phosphate coating was prepared on AZ31 alloy by means of hydrothermal deposition. The results showed that the coating possessed a globular morphology with a long lamellar crystalline structure and a thickness of approximately 40 μm. The surface of the coating became smooth with an increase additive amount of the SnO2 nanoparticles. The corrosion current density and hydrogen evolution rate of the coating prepared in presence of SnO2 were reduced compared to the coating without SnO2 and the bare AZ31 substrate, indicating an improvement in the corrosion resistance of the SnO2-doped coating.

Advances in functionalized polymer coatings on biodegradable magnesium alloys – A review

Magnesium (Mg) and its alloys have become a research frontier in biodegradable materials owing to their superior biocompatibility and excellent biomechanical compatibility. However, their high degradation rate in the physiological environment should be well tackled prior to clinical applications. This review summarizes the latest progress in the development of polymeric coatings on biodegradable Mg alloys over the last decade, regarding preparation strategies for polylactic acid (PLA), poly (latic-co-glycolic) acid (PLGA), polycaprolactone (PCL), polydopamine (PDA), chitosan (CS), collagen (Col) and their composite, and their performance in terms of corrosion resistance and biocompatibility. Feasible perspectives and developing directions of next generation of polymeric coatings with respect to biomedical Mg alloys are briefly discussed. STATEMENT OF SIGNIFICANCE Magnesium (Mg) and its alloys have become a research frontier in biodegradable materials owing to their superior biocompatibility and suitable biomechanical compatibility. However, the principal drawback of Mg-based implants is their poor corrosion resistance in physiological environments. Hence, it is vital to mitigate the degradation/corrosion behavior of Mg alloys for safe biomedical deployments. This review summarizes the latest progress in development of polymeric coatings on biomedical Mg alloys regarding preparation strategy, corrosion resistance and biocompatibility, including polylactic acid (PLA), poly (latic-co-glycolic) acid (PLGA), polycaprolactone (PCL), chitosan (CS), polydopamine (PDA), collagen (Col) and their composite. In addition, functionalized polymer coatings with Mg alloys exhibits a promising prospect owing to their ability of degradation along with biocompatibility, self-healing, drug-delivery and osteoinduction.