High corrosion and wear resistant electroless Ni–P gradient coatings on aviation aluminum alloy parts

A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.

Degradation and biocompatibility of one-step electrodeposited magnesium thioctic acid/magnesium hydroxide hybrid coatings on ZE21B alloys for cardiovascular stents

Constructing a functional hybrid coating appears to be a promising strategy for addressing the poor corrosion resistance and insufficient endothelialization of Mg-based stents.Nevertheless,the steps for preparing composite coatings are usually complicated and time-consuming.Herein,a novel composite coating,composed of bioactive magnesium thioctic acid(MTA)layer formed by deposition and corrosion-resistant magnesium hydroxide(Mg(OH)_(2))layer grown in situ,is simply fabricated on ZE21B alloys via one-step electrodeposition.Scanning electron microscopy(SEM)shows that the electrodeposited coating has a compact and uniform structure.And the high adhesion of the MTA/Mg(OH)_(2)hybrid coating is also confirmed by the micro-scratch test.Electrochemical test,scanning kelvin probe(SKP),and hydrogen evolution measurement indicate that the hybrid coating effectively reduces the degradation rate of Mg substrates.Haemocompatibility experiment and cell culture trial detect that the composite coating is of fine biocompatibility.Finally,the preparation mechanism of MTA/Mg(OH)_(2)hybrid coatings is discussed and proposed.This coating shows a great potential application for cardiovascular stents.

Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.

Advancements in enhancing corrosion protection of Mg alloys:A comprehensive review on the synergistic effects of combining inhibitors with PEO coating

Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical application of Mg alloys is limited due to their high susceptibility to corrosion.Plasma electrolytic oxidation(PEO),or micro-arc oxidation(MAO),is a coating method that boosts Mg alloys'corrosion resistance.However,despite the benefits of PEO coatings,they can still exhibit certain limitations,such as failing to maintain long-term protection as a result of their inherent porosity.To address these challenges,researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys.Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys.Corrosion inhibitors,whether organic or inorganic,can act by forming a protective barrier,hindering the corrosion process,or modifying the surface properties to reduce susceptibility to corrosion.Containers can be made of various materials,including polyelectrolyte shells,layered double hydroxides,polymer shells,and mesoporous inorganic materials.Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation.Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results,demonstrating significant corrosion mitigation,extending the service life of Mg alloy components in aggressive environments,and providing self-healing properties.In general,this review presents available information on the incorporation of inhibitors with PEO coatings,which can lead to improved performance of Mg alloy components in demanding environments.

Micro-aluminum powder with bi-or tri-component alloy coating as a promising catalyst:Boosting pyrolysis and combustion of ammonium perchlorate

A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.

ZIF-8-based micro-arc oxidation composite coatings enhanced the corrosion resistance and superhydrophobicity of a Mg alloy

Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-arc oxidation layer was used as a transition layer to“directly”grow a zinc-based metal-organic framework(MOF)composite coating on the surface of a Mg alloy(AZ91D).Herein,the two zeolitic imidazolate framework(ZIF-8)coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method.The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties,which could prevent the penetration of water and corrosive ions(Cl^(−))into the surface of AZ91D.Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D,and the corrosion current density decreased from 10^(−5)to 10^(−9)A/cm^(2).These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys.Therefore,MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.

Corrosion resistance and anti-soiling performance of micro-arc oxidation/graphene oxide/stearic acid superhydrophobic composite coating on magnesium alloys

Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their potential wide applications.Therefore,a micro-arc oxidation/graphene oxide/stearic acid(MAO/GO/SA)superhydrophobic composite coating with superior corrosion resistance was fabricated on a Mg alloy AZ91D through micro-arc oxidation(MAO)technology,electrodeposition technique,and self-assembly technology.The composition and microstructure of the coating were characterized by scanning electron microscopy,X-ray diffraction,energy dispersive spectroscopy,and Raman spectroscopy.The effective protection of the MAO/GO/SA composite coating applied to a substrate was evaluated using potentiodynamic polarization,electrochemical impedance spectroscopy tests,and salt spray tests.The results showed that the MAO/GO/SA composite coating with a petal spherical structure had the best superhydrophobicity,and it attained a contact angle of 159.53°±2°.The MAO/GO/SA composite coating exhibited high resistance to corrosion,according to electrochemical and salt spray tests.

Graphene-calcium carbonate coating to improve the degradation resistance and mechanical integrity of a biodegradable implant

Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.

ZnO@ZIF-8 core-shell structure nanorods superhydrophobic coating on magnesium alloy with corrosion resistance and self-cleaning

A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidation(MAO) coating as transition layer can effectively enhance the bonding force of the superhydrophobic coating. The semiconductor@metal organic frameworks(MOFs) core-shell structure was synthesized by a simple self-templating method, and obtained ZnO@2-methylimidazole zinc salt(ZIF-8) nanorods array on magnesium(Mg)alloy. ZnO nanorods not only act as the template but also provide Zn^(2+) for ZIF-8. In addition, we proved that the ligand concentration,synthesis time and temperature are the keys to the preparation of ZnO@ZIF-8 nanorods. As we expect, the ZnO@ZIF-8 nanorods array can trap air in the gaps to form an air layer, and the coating exhibits superhydrophobic properties(154.81°). Excitingly, ZnO@ZIF-8 nanorods array shown a superhydrophobic property, without the requirement of fluorination or silane treatment. The results shown that the coating has good chemical stability and self-cleaning performance. Meanwhile, the corrosion resistance has been significantly improved, R_(ct) was increased from 1.044×10^(3) to 1.414×10^(6) Ω/cm^(2) and I_(corr) was reduced from 4.275×10^(-5) to 5.611×10^(-9)A/cm^2. Therefore, the semiconductor@MOFs core-shell structure has broad application prospects in anti-corrosion.

Corrosion resistance and electrical conductivity of V/Ce conversion coating on magnesium alloy AZ31B

A V/Ce conversion coating was deposited in the surface of AZ31B magnesium alloy in a solution containing vanadate and cerium nitrate.The coating composition and morphology were examined.The conversion coating appears to consist of a thin and cracked coating with a scattering of spherical particles.The corrosion behavior of the substrate and conversion coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).Compared with AZ31B magnesium alloy,the corrosion current density of the conversion coating is decreased by two orders of magnitude.The total impedance of the V/Ce conversion coating rise to 1.6×10^(3)Ω·cm^(2)in contrast with2.2×10^(2)Ω·cm^(2)of the bare AZ31B.In addition,the electrical conductivity of the coating was assessed by conductivity meter and Mott-Schottky measurement.The results reveal a high dependence of the conductivity of the coating on the semiconductor properties of the phase compositions.

A super wear-resistant coating for Mg alloys achieved by plasma electrolytic oxidation and discontinuous deposition

Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.

Developing super-hydrophobic and corrosion-resistant coating on magnesium-lithium alloy via one-step hydrothermal processing

Formation of super-hydrophobic and corrosion-resistant coatings can provide significant corrosion protection to magnesium alloys.However,it remains a grand challenge to produce such coatings for magnesium-lithium alloys due to their high chemical reactivity.Herein,a one-step hydrothermal processing was developed using a stearic-acid-based precursor medium,which enables the hydrothermal conversion and the formation of low surface energy materials concurrently to produce the super-hydrophobic and corrosion-resistant coating.The multiscale microstructures with nanoscale stacks and microscale spheres on the surface,as well as the through-thickness stearates,lead to the super-hydrophobicity and excellent corrosion resistance of the obtained coating.

Corrosion resistance of Mg-Al-LDH steam coating on AZ80 Mg alloy:Effects of citric acid pretreatment and intermetallic compounds

In this study,the effects of intermetallic compounds(Mg_(17)Al_(12)and Al_(8)Mn_(5))on the Mg-Al layered double hydroxide(LDH)formation mechanism and corrosion behavior of an in-situ LDH/Mg(OH)_(2)steam coatings on AZ80 Mg alloy were investigated.Citric acid(CA)was used to activate the alloy surface during the pretreatment process.The alloy was first pretreated with CA and then subjected to a hydrothermal process using ultrapure water to produce Mg-Al-LDH/Mg(OH)_(2)steam coating.The effect of different time of acid pretreatment on the activation of the intermetallic compounds was investigated.The microstructure and elemental composition of the obtained coatings were analyzed using FE-SEM,EDS,XRD and FT-IR.The corrosion resistance of the coated samples was evaluated using different techniques,i.e.,potentiodynamic polarization(PDP),electrochemical impedance spectrum(EIS)and hydrogen evolution test.The results indicated that the CA pretreatment significantly influenced the activity of the alloy surface by exposing the intermetallic compounds.The surface area fraction of Mg_(17)Al_(12)and Al_(8)Mn_(5)phases on the surface of the alloy was significantly higher after the CA pretreatment,and thus promoted the growth of the subsequent Mg-Al-LDH coatings.The CA pretreatment for 30 s resulted in a denser and thicker LDH coating.Increase in the CA pretreatment time significantly led to the improvement in corrosion resistance of the coated AZ80 alloy.The corrosion current density of the coated alloy was lower by three orders of magnitude as compared to the uncoated alloy.

Recent progress in self-repairing coatings for corrosion protection on magnesium alloys and perspective of porous solids as novel carrier and barrier

Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.

New superhydrophobic composite coatings on Mg-Mn-Ce magnesium alloy

A novel combined method for the formation of composite coatings on the Mg-Mn-Ce alloy is developed.Ceramic like matrix was formed on the Mg alloy surface by the plasma electrolytic oxidation.Then the samples were subsequently processed by dip-coating in an alcohol suspension of superdispersed polytetrafluoroethylene and spraying with the tetrafluoroethylene telomers solution.SEM,OSP,and SPM was used to study structure of formed surfaces.It was established by measurements of CA and CAH,as well as surface free energy calculations that formed coatings demonstrate superhydrophobic properties due to the presence of an irregular hierarchical surface structure and low surface free energy of fluoropolymers.The coating preserves its hydrophobic properties after exposure to high and low temperatures,for a long time as well as being in corrosive environments.EDS and XRD data analysis confirmed the presence of organofluorine compounds in the composite layers,including in the form of crystalline polytetrafluoroethylene.Using potentiodynamic polarization test and EIS,it was found that the resulting coatings significantly increase the corrosion resistance of Mg material.These data are also confirmed by salt spray tests for 40 days.Incorporation of fluoropolymers additionally decrease coatings coefficient of friction.

Corrosion resistance and mechanisms of smart micro-arc oxidation/epoxy resin coatings on AZ31 Mg alloy: Strategic positioning of nanocontainers

Smart micro-arc oxidation(MAO)/epoxy resin(EP) composite coatings were formed on AZ31 magnesium(Mg) alloy. Mesoporous silica nanocontainers(MSN) encapsulated with sodium benzoate(SB) corrosion inhibitors were strategically incorporated in the MAO micropores and in the top EP layer. The influence of the strategic positioning of the nanocontainers on the corrosion protective performance of coating was investigated. The experimental results and analysis indicated that the superior corrosion resistance of the hybrid coating is ascribed to the protection mechanisms of the nanocontainers. This involves two phenomena:(1) the presence of the nanocontainers in the MAO micropores decreased the distance between MSN@SB and the substrate, demonstrating a low admittance value(^5.18 × 10^(-8)Ω^(-1)), and thus exhibiting significant corrosion inhibition and self-healing function;and(2) the addition of nanocontainers in the top EP layer densified the coating via sealing of the inherent defects, and hence the coating maintained higher resistance even after 90 days of immersion(1.13 × 10^(10)Ω cm^(2)).However, the possibility of corrosion inhibitors located away from the substrate transport to the substrate is reduced, reducing its effective utilization rate. This work demonstrates the importance of the positioning of nanocontainers in the coating for enhanced corrosion resistance,and thereby providing a novel perspective for the design of smart protective coatings through regulating the distribution of nanocontainers in the coatings.

Novel PA encapsulated PCL hybrid coating for corrosion inhibition of biodegradable Mg alloys:A triple triggered self-healing response for synergistic multiple protection

Surface coatings have been extensively used to control the degradation rate of Mg alloys for bioimplant applications.However,these coatings only act as passive barriers.In corrosive media,structural damage impairs their barrier properties,resulting in rapid degradation of Mg alloys.The present study incorporates phytic acid(PA)as a healing agent in polycaprolactone(PCL)microcapsules with a unique honeycomb core matrix to obtain a self-healing PA-PCLcaps coating.The contact between simulated body fluid(SBF)and PA-PCLcaps coated ZM21 exhibited Cassie-Baxter interfacial states,resulting in significant hydrophobicity with a contact angle(CA)of 116.3.The corrosion potential(Ecorr)and current density(Icorr)were found to be-0.28 V and 1.1×10^(-9)A/cm^(2),respectively,for PA-PCLcaps coating,resulting in biosafe corrosion rate of 2.5×10^(-4)mm/year.After mechanical scratching,rapid HA mineralization at scratched regions recovered the hydrogen evolution rate(HER,0.36 mL/cm^(2)/day)and pH change(pH 7.10)of scratched PA-PCLcaps coated ZM21 samples to corresponding unscratched samples within one day of immersion.The coating’s self-healing ability could be attributed to PA released from punctured microcapsules,which facilitates HA chelation.The pH-triggered(pH 10)and Mg(II)-triggered(5 mM)conditions enhanced PA release from PA-PCLcaps coating by 2.5 and 3.1 times,respectively.As a result,dense HA mineralization occurred,which protects the coating from structural defects and ensures its durability in stimulating conditions.The findings of present study provide new insight for design of multiple stimuli-feedback based self-healing coatings on biodegradable Mg alloys.

Pitting corrosion behavior and corrosion protection performance of cold sprayed double layered noble barrier coating on magnesium-based alloy in chloride containing solutions

Nitrogen processed, cold sprayed commercially pure(CP)-Al coatings on Mg-based alloys mostly lack acceptable hardness, wear resistance and most importantly are highly susceptible to localized corrosion in chloride containing solutions. In this research, commercially pure α-Ti top coating having good pitting potential(~1293 mV_(SCE)), high microhardness(HV_(0.025): 263.03) and low wear rate was applied on a CP-Al coated Mg-based alloy using high pressure cold spray technology. Potentiodynamic polarization(PDP) curves indicated that the probability of transition from metastable pits to the stable pits for cold spayed(CS) Al coating is considerably higher compared to that with the CS Ti top coating(for Ti/Al/Mg system). In addition, CS Ti top coating was in the passivation region in most pH ranges even after 48 h immersion in 3.5 wt% NaCl solution. The stored energy in the CS Ti top coating(as a passive metal) was presumed to be responsible for the easy passivation. Immersion tests indicated no obvious pits formation on the intact CS Ti top coating surface and revealed effective corrosion protection performance of the CS double layered noble barrier coatings on Mg alloys in 3.5 wt% NaCl solution even after 264 h.

“Smart”micro/nano container-based self-healing coatings on magnesium alloys:A review

Coating technologies are a commonly used way to protect metals against corrosion.However,with more and more severe service environments of materials,many protective coating systems often are not environmentally friendly or toxic as in the case of chromates.Based on the world’s abundant ideal magnesium(Mg)and its alloy,the smart self-healing anticorrosive coating can autonomously restore the damaged part of the coating according to the environmental changes,strengthen the corrosion protection ability,and prolong its service life.This paper reviews the research progress of smart self-healing coatings on Mg alloys.These coatings mostly contain suitable corrosion inhibitors encapsulated into micro/nano containers.Moreover,the different self-healing mechanisms and functionalities of micro/nano containers are discussed.The micro/nano containers range from inorganic nanocontainers such as mesoporous nanoparticles(silica(SiO_(2)),titanium dioxide(TiO_(2)),etc.),over inorganic clays(halloysite,hydrotalcite-like,zeolite),to organic nanocontainers such as polymer microcapsules,nanofibers,chitosan(CS)and cyclodextrin(CD),as well as,carbon materials such as graphene and carbon nanotubes and hybrids such as metal organic frameworks.The functioning of micro/nano containers can be divided in two principal groups:autonomous(based on defect filling and corrosion inhibition)and non-autonomous(based on dynamic bonds and shape memory polymers).Moreover,multi functionalities and composite applications of various micro/nano containers are summarized.At present,significant progress has been made in the preparation methods and technologies of micro/nano containers.Achieving long-term self-healing properties of coatings sensing of coating failure and early warning after self-healing function failure can be expected as the main development direction of self-healing corrosion protection coatings in the future.

A novel MgF2/PDA/S-HA coating on the bio-degradable ZE21B alloy for better multi-functions on cardiovascular application

Recently, functional molecules such as Polydopamine(PDA), Hyaluronic Acid(HA) and heparin have been widely studied in the field of surface modification of magnesium(Mg) alloy stents for better degradation behavior and biocompatibility, but their further application is limited by undesirable anticoagulant function, uncontrollable degradation and easy bleeding, respectively.Regarding to this consideration, a magnesium Fluoride/Polydopamine/Sulphonated hyaluronic acid(Mg F2/PDA/S-HA) composite coating was successfully prepared by applying S-HA with sulfur content of 9.71 wt% on the surface of ZE21B alloy in this study. The results showed that the composite coating with a unique mesh structure not only inherited the anticoagulant effect of sulfonic acid group and the excellent cyto-compatibility of S-HA with high sulfur content, but also significantly improved the corrosion performance of ZE21B alloy.These results indicate a great application potential of the composite coating in the field of cardiovascular biomaterials.