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The efficiency of the green inhibitors (sodium salts of fumarate, glycolate and gluconate) in suppressing corrosion of the structural MA8 magnesium alloy (MgMnCe) and the biomedical Mg0.8Ca alloy was studied using the hydrogen evolution measurements, mass loss test, EIS, PDP, SVET/SIET. The analysis of the morphology, chemical composition, and growth kinetic of corrosion films formed in 0.9 wt% NaCl solution with and without corrosion inhibitors was carried out. The most compact surface film with the smallest thickness was formed in a saline solution with sodium fumarate. The Mg alloy samples exhibited the highest polarization resistance, the lowest localized electrochemical activity, and the lowest corrosion rate in saline with the addition of sodium fumarate and sodium glycolate. The efficiency of the applied inhibitors was up to 81 %. The model of the corrosion mechanism based on the sorption of molecules of organic inhibitors is proposed. The results show the high compatibility of the used inhibitors with the calcium-phosphate PEO-matrix, indicating the possibility of forming a self-healing coating by means of these active substances.

The present study investigates the physical and chemical characteristics, behavior in vitro and in vivo, and biocompatibility of coatings containing Ta2O5, which are obtained by plasma electrolytic oxidation (PEO) on MA8 magnesium alloy. The obtained coatings demonstrate in vivo biocompatibility and in vitro bioactivity. Compared to the base PEO coating, the layers containing Ta2O5 facilitate the development of apatite in simulated body fluid, suggesting that the inclusion of nanoparticles improves bioactivity of the coatings. It was found that incorporation of Ta2O5 nanoparticles increases roughness and porosity of the formed layers by increasing particle concentration in electrolytes for the PEO process contributing to sufficient soft tissue ingrowth in vivo. Based on in vivo studies, these coatings also provide favorable tissue response and minimal inflammatory reaction in comparison with the bare magnesium alloy due to protection of living tissues from deleterious corrosion events of magnesium implant such as local alkalization and intense hydrogen evolution. The results obtained in the present study concluded biocompatibility, tissue integration of the PEO coatings containing Ta2O5 nanoparticles making them a promising protective layer for biodegradable magnesium implants.

In this study, a calcium-phosphate coating was formed on a Mg–Mn–Ce alloy by the plasma electrolytic oxidation (PEO). The antibiotic vancomycin, widely used in the treatment of infections caused by Staphylococcus aureus (S. aureus), was impregnated into the coating. Samples with vancomycin showed high bactericidal activity against S. aureus. The mechanical and electrochemical properties of the formed coatings were studied, as well as in vitro cytotoxicity tests and in vivo tests on mature male rats were performed. According to SEM, EDS, XRD and XPS data, coatings had a developed morphology and contained hydroxyapatite, which indicates high biocompatibility. The analysis of roughness of coatings without and with vancomycin did not reveal any differences, confirming the high roughness of the samples. During electrochemical tests, an increase in corrosion resistance by more than two times after the application of PEO coatings was revealed. According to the results of an in vivo study, after 28 days of the implantation of samples with calcium phosphate PEO coating and vancomycin, no signs of inflammation were observed, while an inflammatory reaction developed in the area of implantation of bare alloy, followed by encapsulation. Antibiotic release tests from the coatings show a sharp decrease in the concentration of the released antibiotic on day 7 and then a gradual decrease until day 28. Throughout the experiment, no significant deviations in the condition and behavior of the animals were observed; clinical tests did not reveal a systemic toxic reaction.

In this study, the biocompatible protective coating was formed using plasma electrolytic oxidation (PEO) on bioresorbable Mg-0.8Ca alloy. The composition of the formed coating was studied using XRD, SEM-EDX analysis, and micro-Raman spectroscopy. The uniform distribution of hydroxyapatite over the thickness of protective PEO-layer was established. Using traditional (EIS, PDP, OCP) and local scanning electrochemical methods (SVET, SIET with H+-selective microelectrode), the level of protective properties of PEO-layer in a biological environment (mammalian cell culture medium, MEM) was determined. It was established that modification of Mg-0.8Ca alloy surface by PEO contributes to a significant increase in the corrosion resistance of the surface layer, making it possible to control the process of material`s biodegradation. The maximum local electrochemical activity was recorded after 72 h of testing, while for the uncoated sample, intense corrosion degradation was recorded in the first 12 min of exposure to the cell culture medium. Formation of the PEO-coating results in a twofold decrease in the corrosion current density (2.8ˑ10−6 A cm−2) and an increase in the impedance modulus measured at a low frequency (1.7ˑ104 Ω cm2) in comparison with the uncoated material (9.5ˑ10−6 A cm−2; 8.1ˑ103 Ω cm2). The mechanism of material bioresorption was established and a model for biodegradation process of Mg-0.8Ca alloy with hydroxyapatite-containing PEO-coating in MEM was proposed. Analysis of these results and comparing with others obtained by various scientific groups indicate the prospects for application of biocompatible PEO-coating on Mg-Ca alloy in implant surgery.

The high corrosion rate of magnesium and its alloys in chloride-containing solution significantly reduces the potential of this material for diverse applications. Therefore, the formation of a smart protective coating was achieved in this work to prevent degradation of the MA8 magnesium alloy. A porous ceramic-like matrix was obtained on the material by plasma electrolytic oxidation (PEO). Further surface functionalization was performed using layered double hydroxides (LDH) served as nanocontainers for the corrosion inhibitor. Several methods of LDH intercalation with benzotriazole (BTA) were proposed. The composition and morphology of the formed coating were studied using SEM-EDX analysis, XRD, XPS, and Raman microspectroscopy. The corrosion behavior of the coated samples was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization. The corrosion rate was estimated using volumetry and gravimetry methods. The formed composite coating provides the Mg alloy with the lowest corrosion activity (|Z|f = 0.1 Hz = 8.48·105 Ω·cm2, Ic = 1.4·10−8 A/cm2, PH = 0.21 mm/year) and improves the protective properties of the PEO-coated sample (|Z|f = 0.1 Hz = 8.37·103 Ω·cm2, Ic = 4.1·10−7 A/cm2, PH = 0.31 mm/year). The realization of the self-healing effect of the inhibitor-containing LDH/PEO-coated system was studied using localized electrochemical methods (SVET and SIET) with two artificial defects on the surface. A mechanism involving three stages for the active corrosion protection of the alloy was proposed. These findings contribute to the follow-up work of developing modified LDH/PEO-based structures that promote the Mg alloy with high corrosion resistance, superior electrochemical performance for applications in various fields of industry and medicine.

The work provides the results of the one-step formation of boron-containing coatings on an Mg–Mn–Ce alloy by plasma electrolytic oxidation. The results of studies of the composition, structure and morphology of heteroxide coatings are presented. It was established that the boron is contained in the coating mainly in the form of B or B2O3. The introduction of B changes the color of coatings, and also helps to increase their porosity. The method of determining the full cross section of the interaction of thermal neutron absorption efficiency by samples material using the installation of neutron-activation analysis based on 252Cf was developed. It was shown that the introduction of boron into the formed coatings allows to increase the macroscopic cross-section of the interaction of samples with thermal neutrons by 3.8 times. This effect opens the potential for the use of synthesized material in the field of nuclear technologies and aerospace industry.

A comprehensive study of the properties of coatings formed on a magnesium alloy by plasma electrolytic oxidation (PEO) using the electrolytes with nanosized particles of anatase (titanium dioxide) has been carried out. Formed coatings reduce corrosion current density 2.5-fold and increase hardness by 25% compared to a coating without particles. Confocal micro-Raman spectroscopy revealed the presence of anatase and rutile phases in the composition of PEO coating due to the incorporation of TiO2 nanoparticles during plasma electrolytic treatment. The presence of titanium dioxide had a positive effect on the photocatalytic properties of coatings: the constant rate of the methyl orange and methyl blue decomposition is increased in 1.6 and 1.8-fold, respectively, compared to the coating formed in electrolyte without TiO2 particles.

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.

A new method of the formation of composite coatings with the function of active corrosion protection of magnesium alloys was developed using the plasma electrolytic oxidation (PEO) method. Susceptibility of PEO-layers to pitting formation was evaluated using localized electrochemical methods (SVET/SIET). The morphological features and electrochemical properties of composite coatings were studied using SEM/EDX, XRD, micro-Raman spectroscopy and EIS/PDP measurements, respectively. The effect of surface layers impregnation with corrosion inhibitor on their protective properties in a corrosive environment was established. Additional protection was achieved using controllable coating pore sealing with polymer. It was found that the polymer treatment of the PEO-layer does not reduce the inhibitor's efficiency. The formed protective composite inhibitor-and-polymer-containing layers decrease the corrosion current density of a magnesium alloy in a 3 wt.% NaCl solution to three orders of magnitude. This predetermines the prospect of new smart coatings formation that significantly expand the field of application of electrochemically active materials. The mechanism of smart composite coating corrosion degradation was established. The antibacterial activity of the inhibitor-containing coatings against S. aureus methicillin-resistant strain was proved using the in vitro model. These protective layers are promising for reducing the incidence of implant-associated infections.

Today a lot of attention is paid to the formation of thermosensitive systems for biomedical and industrial applications. The development of new methods for synthesis of such systems is a dynamically developing direction in chemistry and materials science. In this regard, this paper presents results of the studies of a new synthesized supramolecular polymer system based on polyethylene glycol and tetrafluoroethylene telomers. The films formed from the polymer substance have the property of switching wettability depending on temperature after heating activation. It has been established that the wettability changes at 60 °C. The contact angle of activated hydrophobic polymer film reaches 143°. Additionally, the system exhibits its properties regardless of the pH of the environment. Based on data obtained by the methods of infrared and x-ray photoelectron spectroscopy, differential thermal analysis and thermal analysis in conjunction with wettability and morphology, a model of the behavior of molecules in a polymer system was built that ensures switching of the hydrophilic/hydrophobic surface state. The resulting polymer system, as well as films based on it, can be used in targeted drug delivery, implantation surgery, as sensors, etc.

The electrochemical behaviour of biodegradable magnesium alloy Mg-0.8Ca was evaluated in a mammalian cell culture medium (MEM) and NaCl solutions (0.9 wt.%, 0.3 wt.%) using traditional (EIS, PDP, OCP) and local scanning electrochemical (SVET, SIET with pH-selective microelectrode) methods at the micro- and meso-level. Corrosion rates of samples in two different media were determined using weight loss tests. The influence of testing media components, alloy composition and microstructure on the material's degradation process was determined. The SVET/SIET test parameters were optimized for in vitro investigation of the bioresorbable material surface. The mechanism of the alloy's bioresorption was suggested. The effect of microsized phases on the corrosion behaviour of the alloy was proved using complementary in situ monitoring and SKPFM measurements. The rapid degradation rate of the alloy is related to the presence of local microgalvanic cells formed by cathodic α-magnesium matrix and anodic Mg2Ca phase. The highest corrosion activity was revealed in the first 12 min of sample exposure to MEM, followed by stabilization of corrosion process due to the material's passivation. Using SEM-EDX analysis, micro-Raman spectroscopy and XPS analysis the composition of the corrosion products was determined. Degradation in MEM proceeds with a formation of magnesium-and-carbonate substituted hydroxyapatite-containing film on the sample's surface. The low possibility of application of Mg-0.8Ca alloy without coating protection in implant surgery was highlighted.

The study considers composite coatings formed on the AlMg3 aluminum alloy, consisting of PEO-coatings impregnated with corrosion inhibitors, 1,2,4-triazole and benzotriazole, in various concentrations. The morphology and composition of the resulting coatings were studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The increase in the protective properties of composite coatings was studied by electrochemical impedance spectroscopy (EIS). SEM-images showed that the coatings have a self-assembled microtubular structure with a tube diameter varying from 300 to 500 nm and average tube height of 9 µm. EIS results showed that samples with composite inhibitor containing PEO-coatings have better protective properties compared to pure aluminum alloy and base PEO-layer. An increase in the concentration of inhibitors of the triazole group from 0.05 M to 0.1 M during impregnation into a PEO-coating leads to a decrease in the corrosion resistance of the samples with composite coatings.

The paper presents the results of the study of corrosion performance of HApcontaining coating obtained on the Mg-0.8Ca bioresorbable magnesium alloy using plasma electrolytic oxidation (PEO). Electrochemical measurements were carried out in minimal essential medium (MEM) using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and monitoring of open circuit potential (OCP) techniques. It was established that the PEO treatment of Mg-0.8Ca leads to a significant increase in corrosion resistance of the material. Formation of heterooxide layer on magnesium alloy contributes to a decrease in corrosion current density (IC) more than three times. The impedance modulus measured at low frequency (|Z|f=0.1 Hz) for a coated material increased by two times compared to an uncoated one.

The coating containing a layered double hydroxide (LDH) was obtained on the MA8 magnesium alloy. The coating morphology, its electrochemical and corrosion behavior were studied. Scanning electron microscopy confirmed the lamellar structure of the LDH. Maps of the element distribution on the surface (the aluminum content on the surface is 3.2 wt.%) and the diffraction pattern of the sample (the presence of a hydrotalcite phase) also confirmed the presence of LDH. The electrochemical and corrosion behavior of the base PEO-coating, an LDH-containing coating, and the LDH-containing coating after impregnation with sodium oleate was compared. According to the experimental data analysis the positive role of LDH in the protection of the magnesium alloy was established. Treatment of the LDH-containing coating with a 0.1 M solution of sodium oleate makes it possible to increase the impedance modulus measured at the frequency of 0.1 Hz by order of magnitude compared to the inhibitor free protective layer. The obtained LDHs have a positive effect on the stability of the protective properties in aggressive medium, which was shown by the decrease in corrosion current density for the investigated sample.

A novel approach to surface modification was developed to improve the corrosion performance of biodegradable magnesium alloys. Additively manufactured magnesium samples and Mg-Mn-based magnesium alloys were used in this study. This method involves the combination of plasma electrolytic oxidation to create a porous ceramic-like matrix, followed by treatment with protective biocompatible agents. The most efficient method for the PEO-layer impregnation using sodium oleate and polycaprolactone was selected and optimized. The correlation between the structure, composition, and protective properties of the hybrid coatings was established. The composition of the formed polymer-containing layers was established using XPS and Raman microspectroscopy. The presence of sodium oleate and its distribution across the coating surface was confirmed at the microscale. The corrosion-protection level of the hybrid layers was assessed using potentiodynamic polarization measurements, electrochemical impedance spectroscopy, hydrogen evolution testing, and gravimetry (mass-loss tests) in vitro. The oleate-containing polycaprolactone layers (HC-SO 0.1–2) demonstrated stable corrosion behavior even after 7 days of immersion in Hank’s balanced salt solution. The corrosion-current density and impedance modulus measured at a frequency of 0.1 Hz for the samples with hybrid coating after 7 days of exposure were equal to 5.68 × 10−8 A∙cm−2 and 2.03 × 106 Ω∙cm2, respectively. The developed method of surface modification demonstrates the coating’s self-healing properties. The effectiveness of employing hybrid anticorrosive bioactive PEO coatings for biomedical products made from magnesium and its alloys was demonstrated.

This paper presents a method of the formation of composite polymer-containing coatings on a Mg–Mn–Ce magnesium alloy by forming a ceramic-like layer using plasma electrolytic oxidation (PEO) and subsequent spraying superdispersed polytetrafluoroethylene suspension. The coating composition and their morphological features were studied by SEM, EDS, GDOES, and XRD. The presented data confirm the embedding of fluoropolymer in the PEO coating. The evaluation of the corrosion properties of the formed composite polymer-containing coatings indicates a decrease in the corrosion current density by more than 3 orders of magnitude in comparison with the base PEO coating. The incorporation of a fluoropolymer in a PEO layer by more than 32% increases the load value at which abrasion of the coating to the substrate occurs and reduces the wear of the coating by more than 27 fold in comparison with the PEO layer. It has been established that composite coatings possess hydrophobic properties: the value of the contact angle attains 152 °.

The protective coating with a self-organized microtubular structure was formed using plasma electrolytic oxidation (PEO) on AlMg3 aluminum alloy in the tartrate-fluoride electrolyte. This protective layer was further modified using corrosion inhibitors of the azole group (1,2,4-triazole, benzotriazole) and polymer material (polyvinilidene fluoride, PVDF). X-ray diffraction analysis and scanning electron microscopy with energy dispersive spectroscopy were used to study the morphology and composition of the obtained oxide coatings. The presence of the inhibitor in the PEO-layer was confirmed using micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The level of corrosion protection of formed coatings as well as the effect of loaded inhibitors on the anticorrosion efficiency was evaluated using electrochemical impedance spectroscopy (EIS) and localized scanning techniques (SVET/SIET). The coating impregnation with corrosion inhibitors of the azole group significantly improves the corrosion characteristics of the material. Impregnation of the base PEO-layer with 1,2,4-triazole during 24 h results in a 36 times increase in the impedance modulus measured at the lowest frequency (|Z|f=0.1Hz). Additional sealing of impregnated coating with polymer improves the corrosion stability of the treated material. On the base of the obtained data, the optimal way of protective inhibitor- and polymer-containing formation using surface treatment was suggested. The best barrier properties were established for hybrid coatings obtained by the immersion of a PEO-coated sample in 1,2,4-triazole solution for 24 h and following spraying the PVDF solution. The value of |Z|f=0.1Hz for this protective layer increased by more than two orders of magnitude in comparison with the base PEO-layer. The three-stage mechanism of corrosion inhibition of the sample with smart inhibitor-containing coating was established.

The increase of corrosion resistance of magnesium and its alloys by forming the smart self-healing hybrid coatings was achieved in this work in two steps. In the first step, using the plasma electrolytic oxidation (PEO) treatment, a ceramic-like bioactive coating was synthesized on the surface of biodegradable MA8 magnesium alloy. During the second step, the formed porous PEO layer was impregnated with a corrosion inhibitor 8-hydroxyquinoline (8-HQ) and bioresorbable polymer polycaprolactone (PCL) in different variations to enhance the protective properties of the coating. The composition, anticorrosion, and antifriction properties of the formed coatings were studied. 8-HQ allows controlling the rate of material degradation due to the self-healing effect of the smart coating. PCL treatment of the inhibitor-containing layer significantly improves the corrosion and wear resistance and retains an inhibitor in the pores of the PEO layer. It was revealed that the corrosion inhibitor incorporation method (including the number of steps, impregnation, and the type of solvent) significantly matters to the self-healing mechanism. The hybrid coatings obtained by a 1-step treatment in a dichloromethane solution containing 6 wt.% polycaprolactone and 15 g/L of 8-HQ are characterized by the best corrosion resistance. This coating demonstrates the lowest value of corrosion current density (3.02 × 10−7 A cm−2). The formation of the hybrid coating results in the corrosion rate decrease by 18 times (0.007 mm year−1) as compared to the blank PEO layer (0.128 mm year−1). An inhibitor efficiency was established to be 83.9%. The mechanism of corrosion protection of Mg alloy via smart hybrid coating was revealed.

Developing anti-icing coatings is an important topic for many scientists. In this work, we describe composite coatings prepared by a combination of plasma electrolytic oxidation and deposition of polytetrafluoroethylene from suspension. The composite layers obtained had high strength and adhesion to metal, which made it possible to use them in extreme environmental conditions. The change in the adhesion strength of ice to the coating surface was considered with various methods for forming composite layers on the surface of the metal and compared with the base PEO layer. The wettability of the resulting coatings as well as the relationship between the contact angle and the ice adhesion strength were evaluated.

Plasma electrolytic oxidation has been used to create a sublayer on aluminum alloy to form a composite coating to improve the corrosion properties of the processed material. The evolution of protective characteristics of the resulting coatings were examined by potentiodynamic polarization during the exposure in a salt spray chamber. The absence of pittings after a 10-day test for the entire series of composite coatings on aluminum alloy confirms the high level of barrier properties of the coated samples.

Surface free energy (SFE) is a crucial parameter for predicting the cell adhesion and proliferation on implantation materials. In this work, the influence of bioactive calciumphosphate coatings on the SFE of titanium and magnesium implants was studied. Results shows that the formation of bioactive coatings increase SFE by 139 % for magnesium alloy and 38 % for titanium, which in turn should have a positive effect on the adhesion and proliferation of osteoblasts.

The paper reveals the changes in corrosion properties of the samples with composite coating subjected to atmospheric corrosion test for 6 months. Composite coating (CC) was formed by treatment of oxide layer obtained by plasma electrolytic oxidation (PEO) with suspension of superdispersed polytetrafluoroethylene microparticles (SPTFE) in polyvinylidenefluoride (PVDF). The corrosion current density was compared for the composite coatings, PEO-coated and untreated samples. It is shown that corrosion current density for the sample with СC tested for 6 months (2.9·10–11 A·cm–2) is more than 3 orders of magnitude lower in comparison with the sample with PEO-layer (3.5·10–8 A·cm–2) and almost 6 orders of magnitude less than for uncoated aluminium alloy (1.7·10–5 A·cm–2).

The paper presents the results of an evaluation of the tribological characteristics of samples with composite coatings during 12 months of atmospheric corrosion. Composite coatings were obtained by treating oxide layer formed by plasma electrolytic oxidation (PEO) with fluoropolymers: superdispersed polytetrafluoroethylene (SPTFE) or polyvinylidene fluoride (PVDF), as well as a suspension of SPTFE in PVDF. It was found that the composite coatings formed in suspension with a ratio of PVDF to SPTFE 1:5 demonstrate the best tribological performance among the studied samples and characterizes by initial coefficient of friction 0.006–0.010. It is shown that samples with composite coatings have 1–1.5 orders of magnitude lower wear rate (9.7∙10⁻5–4.4∙10⁻4 mm3/(N·m)), in comparison with the PEO-treated sample (3.9·10⁻3 mm3/(N·m)).

Metallic biomaterials are widely used for clinical purposes due to their excellent mechanical properties and good biocompatibility. Inspired by the functional surface of natural biological systems, many new designs and concepts have recently emerged to create multifunctional surfaces with great potential for biomedical applications. In present study, bioactive coatings were formed on Mg alloy by plasma electrolytic oxidation (PEO). Morphological features and composition of formed layers were studied by SEM and EDS. It was revealed that PEOcoatings have in their composition Ca and P, which can increase biocompatibility. Moreover, obtained coatings demonstrated high corrosion properties: corrosion current density substantially decreased compared to bare alloy.

We considered coatings obtained on a magnesium based substrate with a different content of a bioactive component, nanosized hydroxyapatite (HAp). The properties of coatings formed by plasma electrolytic oxidation (PEO) in electrolytes containing calcium compounds were compared. Coatings obtained in the electrolyte with HAp demonstrated higher strength characteristics compared to coatings obtained in the glycerophosphate electrolyte. It can be explained by the hardness of the components included in the coating (Mg2SiO4) as well as by the presence of hydroxyapatite nanoparticles. Oxidation of composite samples in an electrolyte with HAp leads to a decrease in the corrosion current density by 2 orders of magnitude compared to this parameter for uncoated samples.