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The corrosion behavior of the TiN monolayer and CrN/TiN multilayer coatings deposited via cathodic arc evaporation physical vapor deposition (CAE‐PVD) on the Ti–6Al–4V substrates were evaluated in Ringer's and Hank's physiological saline electrolytes. XRD (x‐ray diffractometry) and scanning electron microscopy (SEM) analysis were used to characterize the coatings. The corrosion behavior of coatings was assessed by impedance spectroscopy and potentiodynamic polarization techniques. The results showed that the corrosion resistance of coatings was increased in the order of TiN‐Ringer's < TiN‐Hank's < CrN/TiN‐Ringer's < CrN/TiN‐Hank's. Therefore, it can be concluded that the CrN/TiN coating, due to having a large number of interfaces and a smoother surface with fewer macroparticles and pinholes, is more efficient in raising the corrosion resistance properties of titanium than TiN monolayer coating. Moreover, it was observed that Ringer's solution is a more severe environment than Hank's solution. Both coatings, because of the precipitation of a protective corrosion products layer on their surface, showed an enhancement in corrosion resistance with increasing the immersion time from 1 to 14 days in Hank's. The results suggest TiN monolayer and CrN/TiN multilayer coatings as promising candidates for biomedical applications. [ABSTRACT FROM AUTHOR]

In this study, we examined how current density, sodium phosphate concentration, and the addition of copper sulfate to the supporting electrolyte affect PEO coatings on pure titanium. The chemical composition, morphology, and optical behavior of PEO coatings were extensively analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–Vis diffuse reflectance spectroscopy (DRS). With an increase in current density from 6 to 18 A/dm2, the coating's pore size enlarges and the rutile phase content within the coatings increases. The coating created at 12 A/dm2 shows the highest photocatalytic activity and triggers a unique three-stage behavior in the voltage-time diagram. Adding 4 g/l of CuSO 4 to the electrolyte resulted in the formation of an unwanted Cu-based precipitates, causing electrolyte instability. To stabilize it, potassium hydroxide was removed, and the base electrolyte concentration was adjusted. To address this issue, potassium hydroxide was eliminated from the supporting electrolyte. Subsequently, the concentration of the base electrolyte was optimized. Also, the synergistic influence of CuSO 4 addition (4 g/l) to the supporting electrolyte at different concentrations of 5, 10, and, 15 g/l of trisodium phosphate on PA was investigated. The superior photocatalytic performance of the optimum coating created in the electrolyte containing 5 g/l trisodium phosphate and 4 g/l CuSO 4 is attributed to its enhanced porous structure, along with the heterojunction between the anatase and rutile phases. These features significantly boost the available surface area and facilitate the efficient separation and transfer of photogenerated charge carriers. Ultimately, a mechanism for MB photodegradation was proposed based on the findings from Mott-Schottky analysis and DRS. [ABSTRACT FROM AUTHOR]

PEO coatings are formed by subjecting a metal substrate to an electrolytic plasma discharge, resulting in the formation of a porous and rough oxide layer. Herein, the significant role of the chemical composition of the electrolyte system and additives in the formation of an oxide coating on brass alloy in the PEO process was investigated. It was observed that the coating created with 8 g/l aluminate, 1 g/l NaOH, and 1 g/l KF electrolyte had higher homogeneity than other coatings. This is because a composite oxide coating of Cu 2 O, ZnO, and AlCuO 2 was formed. Methylene Blue (MB), a widely used dye in various industries, is known to be persistent and environmentally harmful. The photocatalytic activity of the PEO coating on brass for the removal of MB was investigated under visible light exposure. According to the results, the presence of the sample produced in an electrolyte containing 8 g/l Aluminate, 1 g/l NaOH, and 1 g/l KF resulted in a degradation rate of approximately 65 % for MB photodegradation after 6 h of irradiation. The PEO-coated brass shows promising photocatalytic efficiency compared to our research group's PEO-coated TiO 2 coatings, indicating its potential as a photocatalyst. The results highlight that PEO coating on brass could be a potential candidate for photocatalytic and photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

• PEO or MAO is a coating method that improves the corrosion resistance of Mg alloys, but it has some drawbacks, such as porosity. • PEO coating with inhibitors is a promising solution to improve the corrosion resistance and performance of metallic substrates in various environments. • Inhibitors can be incorporated into the PEO coating or as a separate layer to provide an extra protective barrier against corrosion and extend the lifespan of coated components. • Eco-friendly inhibitors are important for regulations and sustainability. • Green inhibitors or natural compounds can help make coating solutions more sustainable. 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. [ABSTRACT FROM AUTHOR]

This study investigated the influence of three different frequencies (100, 1000, and 2000 Hz) during the PEO process on the characteristics of ceramic coatings fabricated on Ti-6Al-4V alloys in the presence of 12 g/L Na3PO4.12H2O and 3 g/L ZrO2 nanoparticles. The microstructure, surface roughness, wettability, chemical composition, and corrosion performance of the coatings were thoroughly examined to assess their performance. The microstructural results revealed that increasing frequencies led to a reduction in the porosity size, as well as a decrease in coating thickness, wettability, and surface roughness. Additionally, the corrosion performance of the coatings was evaluated in Hank's solution using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods. As the frequency rose from 100 to 2000 Hz, the corrosion current density dropped significantly from 47.35 to 13.75 nA/cm2 and the corrosion potential increased from 218 to 684 mV versus Ag/AgCl electrode. These findings indicated that the coating produced at a frequency of 2000 Hz exhibited the lowest corrosion density, thereby demonstrating superior corrosion resistance compared to the coatings produced at lower frequencies. The corrosion resistance of the optimum coating (coating formed at a frequency of 2000 Hz) was found to be approximately 0.8 times higher compared to the uncoated metal. [ABSTRACT FROM AUTHOR]

WO 3 nanoparticles were grown hydrothermally on porous titania (TiO 2) PEO-coated on Ti in an alkaline electrolyte using pulsed direct current mode. To achieve the best photodegradation of methylene blue (MB) mediated by the PEO/HT hybrid coatings under visible illumination, hydrothermal parameters including precursor concentration, temperature, and time were optimized. In this sense, increasing the Na 2 WO 4 concentration resulted in a decrease in porosity percentage and an increase in average particle size. At an optimal precursor concentration of 0.005 M, the TiO 2 /WO 3 hybrid coating exhibited 67% degradation compared to ∼47% degradation for a bare TiO 2 coating. Based on the LaMer diagram, the growth mechanism of WO 3 crystals under the hydrothermal process was described. The calculated band gap of the PEO/HT coatings reduced from 3.0 eV to 2.68 eV with an increase in W-based precursor content through the hydrothermal process. Consequently, the improvement in photocatalytic performance was attributed to the participation of more WO 3 nanoparticles and the expansion of the light absorption range of TiO 2 up to the visible light range. Increasing the hydrothermal temperature led to an increase in crystallinity and particle size due to growth, but a decrease in porosity. The optimal photocatalytic performance was achieved for the hybrid coatings at a concentration of 0.005 M, with a hydrothermal temperature of 120 °C and treatment time of 18 h, resulting in ∼88% degradation of methylene blue after 360 min of irradiation. The study of photoactivity on a pollutant model indicates that the resulting activity is primarily influenced by the morphology of hybrid coatings, followed by their specific surface area. [ABSTRACT FROM AUTHOR]

The present study aims to explain how the incorporation of anatase TiO2 nanoparticles at three different concentrations, i.e., 1, 3, and 5 g/L, into the ceramic-like oxide plasma electrolytic oxidation (PEO) coatings on pure titanium substrate can affect the friction and wear behavior of the coatings in simulated body fluid (SBF) aqueous solution. For this purpose, a ball-on-disk friction and wear tester was utilized to characterize the wear performance of the PEO coatings. The morphology and dimensions (width and depth) of wear tracks were analyzed by scanning electron microscopy (SEM) and 2D depth profilometry, respectively. The results indicated that abrasive wear was identified in all PEO coatings; however, the coefficient of friction (COF), wear volume loss, and wear rate were strongly affected by the concentration of TiO2 nanoparticles. The coatings containing TiO2 nanoparticles presented a lower COF, less wear volume loss, reduced wear rate, and improved wear resistance due to having smoother surfaces and the presence of hard TiO2 nanoparticles on their surfaces and inside the pores. The coating with 3 g/L of TiO2 nanoparticles demonstrated the lowest wear rate value of 1.33 × 10−6 mm3/Nm (about a 32% reduction compared with that of coating without TiO2 nanoparticles) and the best wear protection properties among all coatings under investigation. The findings suggest TiO2 nanoparticles incorporated PEO coatings as a promising choice of surface treatment wherein the load-bearing capacity of titanium implants is critical. [ABSTRACT FROM AUTHOR]

The present study evaluates the tribological and corrosion behavior of CrN/CrAlN and CrCN/CrAlCN nanostructured coatings applied on 430 stainless steel. These coatings were applied using the physical vapor deposition method from the vapor phase through the cathodic arc technique. X-ray diffraction, field emission scanning electron microscopy, and nano-indentation techniques were utilized for the coatings characterization. Moreover, the adhesion of the coatings to the substrate was evaluated by the adhesion test according to the VDI3198 standard. The corrosion behavior of the coatings was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt % NaCl solution in 24, 72, and 168 h. It was observed that CrN was the major phase in the coatings. The results of the Rockwell C test indicated the good adhesion of both coatings to the substrate. The hardness of CrCN/CrAlCN coating was 20 GPa and CrN/CrAlN coating was 18 GPa. Concerning the friction coefficient, 430 stainless steel, CrN/CrAlN, and CrCN/CrAlCN coatings showed friction coefficients of 1.049, 0.3, and 0.21, respectively. CrCN/CrAlCN exhibited the lowest friction coefficient, which can be ascribed to the higher ratio of H3/E2, higher hardness, and also reduced surface roughness compared to the CrN/CrAlN sample. The R p value of CrCN/CrAlCN coating is higher than that of CrN/CrAlN coating at different times. The corrosion current density of the CrCN/CrAlCN coating was 0.003 μA cm−2 and for the CrN/CrAlN coating, it was 0.057. The obtained results from both corrosion tests are in an agreement and indicate the better resistance of the CrCN/CrAlCN coating against corrosion which can be due to the dense structure, lower roughness, and low wettability of this coating. [ABSTRACT FROM AUTHOR]

In this work, the variation of tribological and corrosion performances of as-deposited and annealed CrN/CrAlN multilayer coatings on 304 stainless steel substrates deposited by the cathodic arc evaporation process was investigated. It was found that annealing resulted in the decomposition of CrN to Cr 2 N. Also, the surface roughness increased as the annealing temperature increased due to the coalescence of macroparticles. Thus, the wettability of annealed samples decreased as the annealing temperature increased. The hardness decreased as the annealing temperature increased due to the increase in the crystallite size. The sample annealed at 400 °C had the lowest wear rate of 3.04 × 10−5 mm3/Nm and 6.4 × 10−5 mm3/Nm in ambient air and Ringer's solution, respectively, due to the optimum ratio of CrN and Cr 2 N, minimum crystallite growth, and optimum adhesion strength. Based on the electrochemical impedance spectroscopy results, the highest corrosion resistance was observed in the specimen annealed at 700 °C, which can be attributed to the existence of Cr 2 N and larger crystallite size in this multilayer coating. [ABSTRACT FROM AUTHOR]

The principal goal of this research is to produce a CrN/Cu multilayer coating and a CrN single-layer coating and also compare their electrochemical and antibacterial behavior. In this investigation, the coatings were applied to the stainless steel substrate by cathodic arc evaporation a sub-division of physical vapor deposition (CAE-PVD). The present phases were characterized and the thickness of the coatings was measured using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Rockwell-C tester was used to evaluate the adhesion quality. Also, to evaluate the mechanical properties of the coatings such as modulus of elasticity and hardness, a nanoindentation test was used and the indentation effect and coating topography were evaluated using atomic force microscopy (AFM). Studying the electrochemical behavior of the coatings was done using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests in Ringer's solution. The results of EIS tests showed that the CrN coating had higher polarization resistance in comparison to the CrN/Cu coating and an increasing trend of polarization resistance related to both coatings was identified by rising the time of immersion. Also, using the PDP curves, the CrN and CrN/Cu coating current densities were estimated at 1.835×10-8 and 2.088×10-8, respectively. The antibacterial activity of CrN and CrN/Cu coatings was evaluated by the spot-inoculation method. The results of the antibacterial test indicated that compared to CrN coating, CrN/Cu coating had a better impact on the control of the bacteria growth. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloys have recently attracted attention in biomedicine as biodegradable materials with non-toxic degradable products. Such compounds have become a frontier in the study of biodegradable materials because of their remarkable biomechanical compatibility and superior biocompatibility. The use of Mg-based implants reduces the negative consequences of permanent biological implants by eliminating the necessity for biomaterial surgery following the healing process. However, the quick deterioration, formation of considerable gas of hydrogen volumes and a rise in the body environment pH are obstacles in the application of Mg as an implant material. Hence, compelling advances for erosion resistance and biocompatibility of magnesium and its alloys are noteworthy. Surface modification may be a practical approach because it improves the erosion resistance compared with extensive preparation of a treated surface for progressed bone recovery and cell attachment. Coating produced by plasma electrolytic oxidation (PEO) seems a compelling method in order to enhance magnesium and the properties of its alloys. PEO-formed coatings cannot provide long-term protection in the physiological environment due to their porous nature. Thus, a polymer coating is applied on the porous PEO-formed coating, which is steadily applied on the surface. Polymer coatings improve the biocompatibility properties of Mg and its alloys and increase corrosion resistance. In this article, the most recent advancements in PEO/polymer composite coatings are reviewed, and the biocompatibility of such coatings is examined. [ABSTRACT FROM AUTHOR]

This study aims to investigate how the predeposition machining processes such as magnetic grinding, turning machining, and wire electrical discharge machining can influence the surface properties including electrochemical and tribological behavior of TiCrN nanostructured coating applied on Mo40 steel substrate. A physical vapor deposition technique using cathodic arc evaporation was used to apply the coating. The crystallographic phases and the microstructure of the coating were studied by X‐ray diffraction and scanning electron microscope, respectively. Rockwell‐C, electrochemical impedance spectroscopy and potentiodynamic polarization, and pin‐on‐disk wear tests were employed to evaluate the adhesion strength, corrosion behavior, and tribological property of specimens, respectively. The electrochemical results after 24 h of exposure to 3.5 wt% NaCl solution showed that TiCrN coating pretreated with a turning process with polarization resistance of about 3525.32 Ω.cm2 had the best corrosion resistance among all specimens. This was because of the improvement of the smoothness, surface quality, and adhesion after the turning process. On the other, the friction coefficient of the grounded sample is less than that of other ones. This is probably due to its higher adhesion strength and higher surface smoothness. [ABSTRACT FROM AUTHOR]

Recently, developing bioactive and biocompatible materials based on Mg and Mg-alloys for implant applications has drawn attention among researchers owing to their suitable body degradability. Implementing Mg and its alloys reduces the risk of long-term incompatibility with tissues because of their close mechanical properties and no need for re-operation to remove the implant. Nevertheless, the degradation rate of the implant needs to be controlled because production of hydrogen gas and accumulation of its bubbles increases local pH around the implants. To confine the integrity of implants and the body, the corrosion concern in the body fluid requires to be addressed. Surface modification as one of the effective strategies can improve corrosion resistance. Besides, it creates a suitable surface for bone grafting and cell growth. The development of proper surface-coated implants needs appropriate techniques and approaches. Plasma electrolytic oxidation (PEO) coating can provide long-term protection by providing a ceramic layer and improving the implant's biocompatibility. Herein, a general review of in-vivo and in-vitro evaluation of PEO coatings on Mg and Mg-alloys has been carried out. Recent advances in surface modification on Mg and Mg-alloys have been discussed, however, the need for reliable laboratory models to predict in-vivo degradation is still valid. [ABSTRACT FROM AUTHOR]

The aim of the present work is to study the CrN single‐layer coating and the Cr/CrN nanolayered coating by cathodic arc evaporation physical vapor deposition (CAE‐PVD) on AISI 304 stainless steel and to assess the electrochemical behavior of the coatings. Field emission scanning electron microscopy (FE‐SEM) and X‐ray diffraction (XRD) were utilized to study the morphology and microstructure of the coatings. The mechanical behavior of the coatings was studied by the nanoindentation technique. The electrochemical behavior of the formed coatings in 3.5 wt.% NaCl solution was investigated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests. Based on the microscopic images, it was realized that both CrN and Cr/CrN coatings were formed having a dense structure on the substrate. The results of EIS measurements showed gradual changes in the polarization resistance of the Cr/CrN nanolayered coating during the immersion time. However, significant changes in the polarization resistance of the CrN single‐layer coating were seen by increasing immersion time comparing with the Cr/CrN coating. The higher polarization resistance of the Cr/CrN coating can be attributed to the effects of the interface between the layers in comparison to the CrN coating. [ABSTRACT FROM AUTHOR]

In this study, to improve the corrosion performance, plasma electrolytic oxidation (PEO) coatings on AZ31B Mg alloy in a phosphate-based electrolyte containing hydroxyapatite nanoparticles were investigated. For this purpose, the corrosion behavior of coatings generated at different frequencies (100, 1000, and 2000 Hz) was studied. The influence of coating frequency on the corrosion behavior of the coatings created as well as the microstructure of the coating was investigated. Surface characteristics of the coatings were investigated using scanning electron microscopy and X-ray diffraction pattern. To investigate the corrosion behavior of coatings generated at different frequencies, polarization and impedance spectroscopy tests in simulated body fluid have been studied. The results showed that at a frequency of 1000 Hz, the created coating had a uniform surface with a lower porosity percentage. Also, the results of electrochemical tests showed that the corrosion resistance of the coating created at a frequency of 1000 Hz leads to the lowest corrosion current density (5.83x10-8 A/cm2) in the coating and thus more became the most corrosion resistant. [ABSTRACT FROM AUTHOR]

In this study, for the first time, the Forsterite (Mg2SiO4) nanoparticles (NPs) with the size of about 25 nm were added to the phosphate-based electrolyte, and the characteristics and properties of the obtained plasma electrolytic oxidation (PEO) coating on AZ31 Mg alloy was investigated. The results of the potentiodynamic polarization measurements revealed that after one week of exposure to simulated body fluid (SBF) solution, the coating with Mg2SiO4 NPs possessed 12.30 kO cm2 polarization resistance, which was more than two times greater than that of the coating without NPs. The thicker coating layer, lower wettability, and also presence of Mg2SiO4 NPs inside the pores were responsible for enhanced corrosion protection in the Mg2SiO4 NPs incorporated coating. After three weeks of immersion in SBF solution, the in-vitro bioactivity test results indicated the ability of the NPscontaining coating to form apatite (Ca/P ratio of 0.92) was weaker than the coating without NPs (Ca/P ratio of 1.17). This could be attributed to the lower wettability of the coating with NPs and supports that the addition of the nanoparticles is not beneficial to the bioactivity performance of the coating. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) and its alloys have received much attention in a lot of areas due to their special chemical and physical properties. Nevertheless, high corrosion rates are a limiting factor. The plasma electrolytic oxidation (PEO) technique is a simple approach to place an oxide film on the surface of light metals like Mg alloys. This method has been considered for controlling the rate of corrosion and improving some other properties. On the other hand, PEO coatings cannot make enough protection of Magnesium alloys for a long time due to porosity and fine cracks. Therefore, PEO-based composite coatings are used to make adequate corrosion protection on the Mg alloys surface. The popularity of these coatings is due to their good corrosion resistance, simplicity, high coating capability, and cost-effectiveness in complex segments. Formation of an organic layer on the surface of PEO coating is one of the effective methods to close the defects and thus prevent the corrosive species penetration into the substrate. Coating the PEO coating with a polymer layer can be a good solution to control the amount of damage and improve the corrosion and abrasion resistance. In addition, PEO coating can eliminate the problems of insufficient adhesion of polymer coatings and is considered as a suitable base for composite coatings. This review paper presents the corrosion and abrasion behavior of the PEO/Polymer dual coating system on Mg alloys. Given the fundamental role of coatings thickness and morphology in wear and corrosion behavior, these aspects have been highly discussed in this study. [ABSTRACT FROM AUTHOR]

To optimize the corrosion, bioactivity, and biocompatibility behaviors of plasma electrolytic oxidation (PEO) coatings on titanium substrates, the effects of five process variables including frequency, current density, duty cycle, treatment time, and electrolyte Ca/P ratio were evaluated. In our systematic study, a Taguchi design of experimental based on an L16 orthogonal array was used. For this, the coatings characteristics such as the surface roughness, wettability, rutile to anatase and Ca/P ratios, and corrosion polarization resistance were investigated. After determining the optimum process variables for each response, the apatite forming ability in SBF (bioactivity behavior) and MG63 cell attachment and flattening (biocompatibility behavior) for two groups of coatings were examined. The first group was optimized based on the maximum corrosion polarization resistance and the variables were set as the frequency of 2000 Hz, the current density of 5 A/dm2, the duty cycle of 30%, the treatment time of 5 min, and the Ca/P ratio of 0.65 at. % in the electrolyte. For the second group, the maximum surface roughness, greatest Ca/P ratio, and highest wettability as well as the minimum rutile to anatase ratio in coatings, could be obtained when the variables were set as the frequency of 10 Hz, the current density of 12.5 A/dm2, the duty cycle of 50%, the treatment time of 12.5 min, and the Ca/P ratio of 1.70 at. % in the electrolyte. The results showed that while both groups of coatings indicated a significant apatite forming ability and can serve as bioactive coatings, a proper attachment and flattening of cells and consequently, the favorable biocompatibility properties were seen only in the first group. [ABSTRACT FROM AUTHOR]

Mg and its alloys are suitable choices for implant materials due to their biodegradability and biocompatibility features. However, the high electrochemical activity of this family of biomaterials results in their fast degradation and severe corrosion in the physiological environment, producing hydrogen (H 2) gas, and therefore increasing the pH of the environment. To meet the clinical requirements, the degradation rate of Mg biomaterials needs to be reduced. Nevertheless, higher corrosion resistance of Mg results in a low alkaline pH, weakening the antibacterial activity. Therefore, while the rapid degradation problem of Mg-based biomaterials needs to be addressed, good antibacterial properties are also necessary. By using the plasma electrolytic oxidation (PEO) surface modification technique, the antibacterial activity of Mg and its alloys can be enhanced while maintaining their corrosion protection properties at a high level. Throughout the PEO process, introducing antibacterial agents into solutions results in a major increase in antibacterial activity of the coatings. Moreover, post- or pre-processing on PEO coatings can provide better protection against bacteria. In this review, the antibacterial activity of PEO coatings applied on Mg and also its alloys will be discussed in more detail. [ABSTRACT FROM AUTHOR]

The main purpose of this investigation was to assess the effect of post-deposition annealing treatment on the electrochemical behavior of TiN coating developed on AISI 304 stainless steel substrate using cathodic arc evaporation physical vapor deposition (CAE-PVD). Post-annealing treatment at 400°C was performed on the coated substrate for 1 h. The studied samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The preferred orientation of TiN (111) was verified by XRD patterns. The crystallinity of the coating was increased after annealing treatment. SEM observations indicated that TiN coatings free of cracks were developed on the substrate. The electrochemical measurements elucidated that the annealed coating had better corrosion resistance compared to that of the as-deposited coating with a lower current corrosion density. This investigation implies that improved corrosion performance of the TiN coating can achieved by performing post-deposition annealing treatment. [ABSTRACT FROM AUTHOR]

In this paper, the plasma electrolyte oxidation (PEO) technique was applied to modify the AZ31B Mg alloy surface. Effects of various concentrations of ZnO nanoparticles into an electrolyte with nanoparticles of hydroxyapatite (HAp) on the antibacterial and corrosion behavior of coatings were studied. Potentiodynamic polarization tests were done in Ringer's electrolyte to study the coatings corrosion behavior. Results of XRD indicated that the provided PEO films mostly have phases of HAp, MgO, and Mg3(PO4)2 and ZnO. The results indicated that increasing the concentration of ZnO nanoparticles raised the thickness, roughness, and wetting angle and also enhanced the coatings antibacterial activity. The inhibition percentage of bacterial growth for the specimen with the highest concentration of nanoparticles (4 g/L) after 6 h against E. coli and S. aureus was 23.5% and 45.5%, respectively. The concentration of nanoparticles had no major effect on the porosity size of the ceramic coating. Moreover, adding ZnO nanoparticles declined the corrosion current density and raised the corrosion potential with regard to the metal substrate. The formed coating in the solution containing 1 g/L ZnO nanoparticles had the highest corrosion behavior among all of specimens that led to a 970 multiplication corrosion resistance of AZ31B Mg alloy. [ABSTRACT FROM AUTHOR]

In this study, TiN coatings were deposited on Ti-6Al-4V alloy surface using cathodic arc evaporation (CAE) deposition process at three different bias voltages (-150, -200 and -250 V) applied to the substrate. In this regard, the effect of bias voltage on the microstructure and corrosion behaviour of coatings was studied. The microstructure of the coated specimens was analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). The corrosion behaviour of the coatings was studied by potentiodynamic polarization (PDP) experiments and electrochemical impedance spectroscopy (EIS) in the simulated media. Studies on SEM images showed that formed coatings at bias of -200 V exhibited the least amount of needle like cavities (0.4%) and macroparticles. Studying the effect of bias voltage on the corrosion behaviour of the coatings deposited at three bias voltages showed that the maximum corrosion resistance was obtained at -200 V and this voltage had the least current density in polarization measurements (5.59× 10-7 A/cm2). So, it was considered as the optimal bias voltage. [ABSTRACT FROM AUTHOR]

The goal of this research is to determine the effect of N2 pressure to argon pressure on the microstructural analysis and corrosion behavior of nanostructured TaN deposited coatings using a reactive DC‐magnetron sputtering (RDCMS) technique. The samples coated microstructure was studied by the X‐ray diffraction (XRD) and scanning electron microscope (SEM), and elemental distribution was studied using energy‐dispersive X‐ray spectroscopy (EDS). To investigate the corrosion behavior of nanostructured TaN coatings, the potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests were performed in Hank's physiological solution. The results of different tests revealed that the coating with a content of 17.6% PN2/PAr consisted of hexagonal and orthorhombic TaN phases and had denser microstructure and free pores. This coating showed superior corrosion behavior in comparison to the other ones. Also, the corrosion resistance of this coating raised by increasing the time of immersion from 48 to 168 h. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the tribological and corrosion behavior of TiN/CrN nanostructured multilayer coating on H13 carburized hot-work tool steel. Pack cementation and cathodic arc physical vapor deposition (Arc-PVD) techniques were employed to apply adiffused layer and ahard coating, respectively. FE-SEM and XRD were used for coating characterization. Apin-on-disc wear test and Rockwell Cindenter were employed to study wear behavior and adhesion of the coating. To evaluate the corrosion behavior of the specimens, the specimens were tested by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) after immersion in 3.5% sodium chloride solution for 48 hours. The results of potentiodynamic polarization and EIS curves showed that the TiN/CrN nano-layer coating with apre-carburized treatment demonstrated abetter corrosion behavior than H13 and carburized samples. According to the electrochemical test, the current density of the substrate, carburized, and pre-carburized TiN/CrN coated samples were 1.070, 0.875, 0.487 µA/cm2, respectively. This improvement in corrosion resistance is due to the high density of the TiN/CrN nano-layers coating that prevents the diffusion of the corrosion solution into the substrate. [ABSTRACT FROM AUTHOR]

Biomaterials are substances of artificial or natural origin that are used to improve, treat, heal or replace the tissue or bone of a human or animal body. Due to the ever-increasing progress and the widespread use of biomaterials for various biomedical purposes, different methods are used to modify their surface characteristics. One of the problems facing biomaterials such as implants, prostheses, and stents is the presence of various bacteria that can cause adverse side effects such as infection, swelling, and tenderness. This raises the issue of their resistance to bacterial infection, a subject that needs to be thoroughly investigated. So far, a variety of methods have been developed to treat or coat biomaterials and make them resistant to bacterial infections. One of the most promising approaches is the plasma electrolytic oxidation (PEO) process. This process is not only successful in the formation of porous, hard, corrosion-resistant, wear-resistant, and biocompatible coatings but also can be easily manipulated to introduce antibacterial agents to the coatings structure. The addition of nano- or micro-sized particles in the electrolytes has been proven to not only modify the composition and structure of the PEO coatings, but also bring about a strong antibacterial activity. In light of recent advances in this field, the following review aims at discussing different aspects of particles addition in PEO electrolytes when the antibacterial activity is the main concern. [ABSTRACT FROM AUTHOR]

The plasma electrolytic oxidation (PEO) procedure is utilized in order to amend the surface properties of Mg and its alloys. This procedure creates a ceramic coating on the surface applying high-voltage. The presence of deep pores and porosities in the surface that affect the corrosion resistance of the coatings is one of the PEO procedure limitations. One of the useful methods to decrease porosities of coating and improve its final properties is changing electrolyte conditions based on the presence of micro- and nanoparticles. The present paper reviews the mechanisms of particle adsorption and composition in PEO thin films in addition to the effect of particle addition on the microstructure, composition and corrosion behavior of coatings that were applied on magnesium alloys. [ABSTRACT FROM AUTHOR]

The aim of this research is the evaluation of the influence of TiN, CrN and TiN/CrN nanostructured coatings on corrosion resistance of nickel-chromium dental alloy in artificial saliva environment with two pH levels (3.0 and 6.5). Nickel-chromium alloy tested in this study were more resistant to corrosion in artificial saliva conditioning media when coated with different types of coating materials, as compared to uncoated alloy. The electrochemical measurements propose that the alloy with CrN coating has shown a high corrosion resistance in different pH levels. The superior passivation of CrN monolayer coating in modified Fusayama artificial saliva solution may be concluded from two essential factors, passive range, and corrosion current density. The passive range is well-developed, while the corrosion current density is much lower if compared to the other groups. Also, the Nyquist and polarization plots reveal that TiN, CrN and TiN/CrN nanostructured coatings have an excellent corrosion resistance which is considered much higher if compared to the substrate. The values of corrosion current density for CrN nanostructured coating in artificial saliva environment with two pH levels of 3.0 and 6.5 were 1.373 × 10−8 and 5.416 × 10−8 A.cm−2, respectively that were the lowest corrosion current density values among the other samples. [ABSTRACT FROM AUTHOR]

In this study, plasma electrolyte oxidation (PEO) method was employed to modify the surface of Ti–6Al–4V. Effects of different concentrations of ZrO 2 nanoparticles (0, 1, 3 and 5 g/l) into a phosphate-based electrolyte on the morphology, wettability, antibacterial and corrosion behaviors of coatings were investigated. Microstructural analyses of coatings were evaluated using scanning electron microscopy with an energy dispersive spectrometer. Also, X-ray diffraction, contact angle instrument and profilometry were respectively used to perform phase analysis, wettability, and surface roughness of the coatings. The antibacterial test was conducted with spot inoculation method on four pathogenic bacteria. Polarization and impedance spectroscopy measurements were performed in Hank's solution to investigate the corrosion behavior of coatings. The results revealed that PEO coatings without nanoparticles and by increasing the concentration of the ZrO 2 nanoparticles up to 3 g/l in the electrolyte led to a significant improvement in the antibacterial activities of gram-negative bacteria (P. aeruginosa and E. Coli). In the case of gram-positive bacteria, the PEO coated samples demonstrated improved antibacterial effects but addition of ZrO 2 nanoparticles in the PEO coatings resulted in deterioration of antibacterial effect. The sample coated with 3 g/l ZrO 2 nanoparticles showed the peak corrosion resistance compared to its counterparts. [ABSTRACT FROM AUTHOR]

The main goal of this study is to compare the electrochemical behavior of CrN/TiN multilayer coating and TiN single-layer coating applied by cathodic arc evaporation (CAE) -physical vapor deposition (PVD) on the substrate of Ti-6Al-4 V in Hank's solution. So, a TiN single-layer coating was formed using PVD method as well as CrN/TiN multilayer coating under totally the same conditions including deposition temperature, working pressure, bias voltage, cathode current and deposition time. To identify the phases in the coatings, X-ray diffraction (XRD) was utilized in order and field emission scanning electron microscopy (FE-SEM) was used in order to study the microstructure of coating. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests were also carried out for corrosion measurements. In the corrosion evaluation, the PDP and EIS tests were performed for the samples after immersion in Hank's solution for 24 hours to reach the steady state. The obtained results from PDP curves showed that the specimen with CrN/TiN multilayer coating exhibited better corrosion behavior than the TiN single-layer coatings. This improvement in corrosion resistance is probably due to the high density of the layers in the CrN/TiN multilayer coating that prevents the penetration of the corrosive solution to the substrate. [ABSTRACT FROM AUTHOR]

In this study, a zirconium nitride/chromium nitride nano-multilayer coating was deposited on AISI 304 specimen using cathodic arc evaporation-physical vapor deposition (CAE-PVD). The characterization of the samples were evaluated by scanning electron microscopy (SEM), field emission-SEM (FE-SEM), and X-ray diffraction (XRD). To evaluate effect of immersion time on the electrochemical behavior of ZrN/CrN nano-multilayer coating using electrochemical impedance spectroscopy (EIS) measurements were carried out in 3.5 wt. % NaCl media. Using the CAE-PVD method, nano-multilayer ZrN/CrN coating with high adhesion and density was successfully produced. A unique high polarization resistance of ZrN/CrN nano-multilayer coatings in comparison to AISI 304 stainless steel without coating was made. As well as the desirable behavior corrosion results showed that in the ZrN/CrN nano-multilayer coating to the AISI 304 substrate within the 3.5 wt. % NaCl, there is a barrier against corrosive agents that is preventing corrosion occurrence. The SEM images disclosed that there were not any pits or severe damages on the surface of the ZrN/CrN nano-multilayer coating. The FE-SEM micrographs show that the coating structure contains alternate layers of ZrN and CrN. The energy dispersive spectroscopy (EDS) analysis and x-ray map were disclosed elements distribution in the cross-section of the nano-multilayer coating. [ABSTRACT FROM AUTHOR]

The present work has studied the effect of sodium fluoride on properties of plasma electrolytic oxidation (PEO) coatings. PEO coatings were formed on 6061 Al alloy in aluminate based electrolytes with different sodium fluoride concentrations. The results indicated that addition of sodium fluoride to the electrolyte prepared ceramic coating with high quality and therefore improved the corrosion resistance in 3.5 wt% NaCl solution. Scanning electron microscopy (SEM) images were used to examine the cross sectional and surface morphology of the coatings. The corrosion behavior of the PEO coatings were evaluated using electrochemical impedance spectroscopy (EIS). The corrosion behavior of the coatings improved by adding 1 g/L sodium fluoride into the electrolyte, but the corrosion resistance of the coatings decreased while adding more than 1 g/L sodium fluoride in electrolyte solution. The prepared sample in the electrolyte with 1 g/L sodium fluoride showed the best morphology with the least porosity and more corrosion resistance compared with other coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] • The TiO 2 -CuO nanocomposite coatings were successfully produced via the PEO technique on the Ti substrate. • Influence of the ionization process on the incorporation of CuO nanoparticles into PEO coatings was discussed. • The CuO-ionized coating is more efficient in TC photodegradation than the coating containing unmodified CuO nanoparticles. • The synergistic effect of Cu2+, Cu(OH) 2, and CuO on the photocatalytic performance after the ionization process was proved. • The mechanism and pathway of TC photodegradation were fully addressed. • The photostability of CuO-incorporated coating was proved after 5 cycles. In this study, copper oxide-embedded TiO 2 coatings were introduced on pure titanium via plasma electrolytic oxidation (PEO), which exhibited photocatalytic capacity for tetracycline (TC) degradation. Moreover, the impact of the ionization process and its temperature on the photocatalytic efficiency were investigated. All coatings containing CuO nanoparticles (NPs) exhibited finer micropores, higher specific areas, and higher wettability. The phase analysis results prove that coatings containing CuO NPs are composed of anatase and CuO phases, whereas the addition of ionized CuO NPs into the electrolyte leads to the formation of anatase, rutile, CuO, TiP 2 O 7, and Cu(OH) 2. All the CuO-incorporated coatings resulted in highly efficient TC photodegradation, the highest of which was 70 % for the coating containing 1 g/L CuO NPs. Most importantly, the introduction of 1 g/L CuO -ionized NPs at 25 °C increased the photocatalytic efficiency to 92 %, whereas increasing the ionization process to 60 °C significantly decreased the photocatalytic activity to 60 % after 6 h of visible light illumination. Moreover, the optimum coating satisfied the photocatalytic efficiency requirement even after five cycles. An in-depth investigation of the effect of photocatalytic parameters, including the concentration and pH of pollutants, as well as the light intensity, was also performed. Appropriate scavenger tests were employed to examine the impact of different reactive oxygen species and photocatalytic mechanisms. Finally, based on the intermediate products, a probable TC photodegradation pathway was suggested. [ABSTRACT FROM AUTHOR]

In this work, KOH, Na 2 SiO 3 and Na 2 B 4 O 7 were used as electrolytes for pulsed DC micro-arc oxidation (MAO) process. We studied the effect of KOH concentration of these electrolytes on the microstructure, chemical composition, and electrochemical behavior of pulsed DC MAO coatings formed on AZ31B Mg alloy. The surface characteristics of the coatings have been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). All electrochemical measurements revealed that pulsed DC MAO process significantly improved the electrochemical behavior of AZ31B Mg alloy. Moreover, these measurements revealed that the sample 3 (1.5 M KOH) exhibited the best electrochemical behavior which resulted in high corrosion resistance compared to that of the other MAO treated samples. This behavior is attributed directly to the pore size, porosity percentage and micro-cracks. According to SEM micrographs, with increasing KOH concentration from 0.5 M to 1.5 M, the average pore size and porosity percentage decrease. However, increasing the concentration from 1.5 M to 2.0 M causes deleterious influence on the average pore size and micro-cracks. [ABSTRACT FROM AUTHOR]

CrN/CrAlN multilayer coatings were deposited on AISI 304 stainless steel substrates utilizing the CAE-PVD process. Then the coatings were annealed at 400, 500, 600, and 700 °C for a duration of 1 h in a vacuum condition. The phases identification, surface morphology, mechanical properties, adhesion, and corrosion behavior of the coating before and after post-deposition annealing treatment were characterized using XRD, SEM, nanoindentation test, Rockwell-C adhesion measurements, and EIS assays, respectively. The results indicated that with increasing post-deposition annealing treatment temperature, the phase structures of the multilayer coating vary from a face-centered cubic CrN to a hexagonal Cr 2 N. Moreover, annealing resulted, in the decrease of the macroparticles on the coating surface decreased. The hardness of the multilayer coating decreased from 19 GPa to 17 GPa, which can be ascribed to the increase in crystallite size and the decrease in the residual stress and annihilation of defects as the temperature increased to 700 °C. Based on the EIS results, the sample annealed at 700 °C had the highest corrosion resistance among other samples, which can be attributed to a decrease in the porosities as corrosion initiation sites, the existence of Cr 2 N as corrosion resistance phase, and an increase in the crystallite size of the multilayer coating. • Comprehensive evaluation on the effect of annealing on CrN/CrAlN multilayer coating. • Significant decrease in residual stress and macrostrain. • Crystallite growth resulted in the decrease in the hardness of the coating by 10%. • Enhancement of electrochemical properties through post-deposition annealing. [ABSTRACT FROM AUTHOR]

The poor biological performance of zirconium implants in the human body resulting from their bio-inertness and vulnerability to corrosion and bacterial activity reflects the need for further studies on substitution or performing the surface modification. The suggestion of employing zirconia (ZrO 2) bioceramic coatings for surface modification seems beneficial. This systematic review aims to identify and summarize existing documents reporting the biological responses for ZrO 2 coatings produced by the PEO process on zirconium implants. PubMed, Scopus, and Web of Science international databases were searched for the original and English-language studies published between 2000 and 2021. All publications reported at least one study about in-vitro (cellular and immersion studies), in-vivo (animal studies), and antibacterial topics for ZrO 2 -PEO coated zirconium implants. Throughout the initial search, 496 publications were found, and 296 papers remained following the elimination of duplicates. Finally, after multiple screening and eligibility assessments, 25 publications were qualified and included in the review. Among them, 25 in-vitro (cellular and immersion in SBF and Hanks' solutions studies), one in-vivo (animal studies), and eight antibacterial studies were found. The ZrO 2 coated samples demonstrate no cytotoxicity, high cell viability rate, and excellent biocompatibility. However, changing the solution composition and electrical parameters during the PEO procedures result in significant changes to in-vitro responses. As an instance, the ZrO 2 coating surface demonstrates greater biocompatibility after irradiated by UV, which makes the surface more suitable for cell growth. Due to weak apatite-forming ability, the zirconium sample shows low bioactivity in SBF. However, most cases (13 out of 16) show that the specific morphology and chemical composition of the ZrO 2 coating promote apatite-forming ability with good bioactivity in SBF. Nevertheless, few papers (three out of 16) showed that the ZrO 2 coatings immersed in SBF had no apatite precipitates and so no bioactivity. These cases limit the bioactivity enhancement to treatment by UV-light irradiation, hydrothermal and chemical treatment, thermal evaporation, and cathodic polarization post-treatment on ZrO 2 coatings. Both zirconium and ZrO 2 coated samples do not show apatite-forming ability in Hanks' solution. The ZrO 2 coated implant with the bone together indicates a greater shear strength and rapid new bone formation ability during 12 weeks because of containing Ca-P compounds and porous structure. The UV post-treated ZrO 2 coating induces faster new bone formation and firmer connection of bond with bone than those of untreated ZrO 2 coatings. A stronger antibacterial activity of ZrO 2 coatings is confirmed in half of the selected papers (four out of eight studies) compared to the bare zirconium samples. The antibacterial protection of ZrO 2 coatings can be influenced by the PEO procedure variables, i.e., solution composition, electrical parameters, and treatment time. In three cases, the antibacterial activity of ZrO 2 coatings is enhanced by deposition of Zn, Ag, or Cu antibacterial layers through thermal evaporation post-treatment. [ABSTRACT FROM AUTHOR]

Abstract In this work, different electrochemical analyses in Ringer's solution at 37 °C were implemented to understand the electrochemical response of diversity of titanium boride coatings developed on the commercially pure titanium (CP–Ti) via pack cementation method. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images indicated that the boriding creates the TiB whiskers and TiB whiskers/TiB 2 dense layer on the top of the surface of CP–Ti in respect to the heat-treatment at 900 and 1000 °C for 3 h. Potentiodynamic polarization curves cleared the passive behavior of the borided samples. Electrochemical impedance spectroscopy (EIS) assays revealed the satisfactory corrosion resistance of the borided samples in Ringer's solution. Mott–Schottky (M–S) assessments represented that the passive films formed on CP–Ti and the borided samples behaved as doped n-type semiconductor properties. Furthermore, M–S assessments indicated that the donor concentration of the passive films decreased with increasing the time. Finally, the borided sample at 900 °C in comparison with the borided sample at 1000 °C illustrated to be the more suitable selection for bioimplant applications, mainly due to better surface conditions to form a less defective and more protective passive film. Highlights • Boriding of Cp-Ti at 900 and 1000 °C for 3 h forms TiB and TiB/TiB 2 , respectively. • The better electrochemical performance was observed for borided samples. • TiB coating has better in-vitro electrochemical behavior than TiB/TiB 2. • Borided sample at 900 °C represents the highest polarization resistance. • Passive films formed on all samples behave as n-type semiconductor. [ABSTRACT FROM AUTHOR]

Recently, high power impulse magnetron sputtering (HIPIMS) technique has been widely applied to deposit hard coatings such as Ti-based coatings on industrial tools due to its strong merits of high coating density, smooth surface, and excellent adhesion. In this work, TiN (Titanium Nitride) nanostructured coatings were deposited by two different methods (HIPIMS and DCMS techniques) with constant processing parameters and their electrochemical behaviors were investigated in a 3.5% NaCl solution. X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), and atomic force microscopy (AFM) were used to characterize and evaluate the coatings composition, surface morphology, and surface roughness, respectively. It is found that the preferred orientation depends on the applied deposition technique. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) were used to compare the electrochemical responses of these nanostructured coatings in 3.5% NaCl solution. The results indicate that HIPIMS-TiN coating is of well-defined denser nanocrystalline structure, which not only is smoother but also has a superior passivation and better protects the substrate against the ingress of aggressive anions. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the mechanical and tribological behavior of chromium nitride (CrN) single layer and multilayer nanostructured coatings of chromium/chromium nitride (Cr/CrN) applied on AISI 304 stainless steel to be used in a marine application. CrN and Cr/CrN coatings were performed using cathode arc evaporation a division of physical vapor deposition (CAE-PVD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM) were utilized for phase identification of coatings and surface morphology, respectively. Nano-indentation method was used to investigate the mechanical behavior of coatings. The tribological behavior of the coatings was studied by the ball-on-disk method. The results indicate that the mechanical behavior of the Cr/CrN multilayer nanostructured coatings is better in comparison to the CrN single-layer coatings. The hardness values of CrN and Cr/CrN coatings were 21.5 and 23.3 GPa, respectively. The higher hardness of the nanolayered coating might be owing to blocking the movement of dislocations and microcracks by its layered structure. Furthermore, the tribological behavior of AISI 304 stainless steel was highly amended by applying the coatings. The coefficient of friction for CrN and Cr/CrN coatings in a dry condition decreased from 0.61 to 0.49 and 0.46, respectively. Also, the CoF value reduced from 0.57 to 0.38 and 0.37 in 3.5 wt% NaCl electrolyte. The lower friction coefficient of the Cr/CrN multilayer nanostructured coating is perhaps due to its higher hardness and lower roughness. • The elastic modulus and hardness value of the Cr/CrN multilayer coating are higher than these of the CrN coating. • The effect of Cr/CrN multilayer coating on improving the tribological properties is more in comparison to CrN coating. • A higher corrosion resistance for the Cr/CrN coating comparing to CrN coating can be ascribed to the layered architecture. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of critical implant pretreatment parameters are reviewed. • Nanoparticle addition and duplex treatment dominate antibacterial PEO coatings. • Bacteria-killing methods like contact, release, trap and photocatalysis are discussed. • Photocatalytic and release killing of PEO coatings investigation is extremely needed. Ti and Ti-alloys are widely utilized as suitable biomaterials for implants, since they present good biocompatibility and mechanical properties. However, they can be an ideal substrate for bacteria attachment, promoting biofilm infections. Biomaterial-associated infections is one of the major healthcare challenges that is currently faced by humanity. This fact causes increased morbidity and distress in patients, along with high economic costs due to increased hospitalizations. There are several strategies to overcome the biofilm infection associated to implants, especially plasma electrolytic oxidation (PEO) process. PEO is highly effective in the production of hard, porous, wear- and corrosion-resistant, as well as biocompatible coatings. Additionally, this method can be applied to introduce antibacterial coatings, with the most prevalent ones being bacteria-killing and bacteria-repelling. Thus, in this review, the biofilm formation implications in implants are presented, as well as the antibacterial mechanisms presently known. The effect of PEO on the antibacterial ability of Ti and Ti-alloys will then be discussed in detail. Finally, the PEO procedure parameters and modifications that lead to high performance of antibacterial implants will be presented. [ABSTRACT FROM AUTHOR]

• The PEO coatings are produced with TCP addition to modify the surface morphology. • The calcium-phosphate PEO coating demonstrates enhanced wettability properties. • The PEO coating improves the bedding surface to facilitate apatite compound formation without compromising corrosion protection. [Display omitted] Recently, Mg alloys have found appealing biomedical applications because of properties such as biodegradability and biocompatibility. However, the full potential of Mg alloys has yet to be exploited as implant materials due to insignificant corrosion resistance and inadequate support to contain apatite compounds. This study presents a novel method to prepare and modify plasma electrolytic oxidation (PEO) coatings facilitating the formation of apatite compounds on the surface without compromising corrosion protection. We prepared calcium-phosphate PEO coatings in a phosphate-based electrolyte benefiting from introducing tricalcium phosphate (TCP) salt as an additive. The composition and surface morphology of coatings produced with the addition of 1–4 g/l TCP were studied using EDS, XRD, FT-IR, and FE-SEM. Moreover, coatings' surface roughness and wettability were evaluated. We investigated the electrochemical behavior of coatings exposed to simulated body fluid (SBF) at four intervals (1 h, 1, 3, and 7 days) using electrochemical impedance spectroscopy (EIS). We realized that the coating produced with 4 g/l TCP addition offers a modified surface supporting the bedding for precipitation of apatite compounds and demonstrating significant corrosion protection. [ABSTRACT FROM AUTHOR]