Anodic Treatment Research Articles

Corrosion resistance of 5005 aluminum alloy by anodizing treatment in a mixture of phosphoric and boric acids

The corrosion resistance of 5005 aluminum alloy was improved by anodizing treatment in a mixture electrolyte of phosphoric acid and boric acid. The influence of anodizing parameters on the corrosion resistance of the studied alloy has been investigated. For example, the effect of the concentration of phosphoric acid, concentration of boric acid, voltage and time of anodization. In this work, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were used to study the corrosion behavior of the aluminum alloy. Scanning electron microscopy (SEM) method was used to study the surface of the aluminum alloy before and after anodization. The obtained results show that the anodizing treatment of 5005 aluminum alloy in phosphoric-boric acids provides better corrosion resistance in comparison with the anodizing treatment in phosphoric acid.

(Invited) Recent Advances in Structural Engineering of Nanoporous Anodic Alumina and Applications

In the last years structurally engineered nanoporous materials have attracted an increasing interest due to their potential applications in different research fields such as nanophotonic, biotechnology, sensing, catalysis, drug delivery, tissue engineering, batteries, membrane separation, and so on. Among other, nanoporous anodic alumina (NAA) has become an interesting material as a result of their outstanding set of properties, cost-competitive fabrication processes and fully scalable process compatible with conventional micro- and nanofabrication technology.Nanoporous anodic alumina is obtained by the electrochemical etching of aluminum. Under specific anodization condition presents a self-ordered hexagonal pore distribution of parallel cylindrical nanopores with pore diameters between 5 and 300 nm. Its geometric characteristics such as pore diameter, pore length and separation distance can be tuned by the anodization conditions (voltage, current density, temperature and electrolyte concentration) [1-2]. Their chemical resistance, thermal stability, and intrinsic photoluminescence are some of the outstanding properties of NAARecently, different anodization and post-anodization treatments (etching and annealing) have been developed to create new structures and pore geometries such as modulated, funnel-like, serrated-like, tip-like, etc. The application of periodic variations of current or voltage during the anodization is transferred to the material as the periodic variation of the pore diameter and consequently, it is possible design, 2D and 3D structures. In particular, it is very interesting the design photonic structures with tunable stop bands within the UV-VIS-NIR range by applying cycling anodization processes [3-4]. Another interesting example of structural engineering is the fabrication of anodic alumina nanotubes by pulse anodization performed in galvanostatic conditions. The length of nanotubes and inner and outer diameters are tailor-engineered by varying pulse period and current density level [5].In addition, its effective surface area makes of NAA an interesting platform for sensing and loading and releasing of active agents. For example, the surface of NAA can be easily functionalized to be selective for specific molecules and covered with biodegradable, chemical, or pH responsive agents to trigger and regulate the release. Another approach is to decorate the surface with magnetic or metallic nanoparticles. The surface modification of nanoporous anodic alumina can provide new properties and functionalities that can be advantageously used besides the structural engineering for innovative applications.In this talk, we will present recent advances in the design and fabrication of nanostructures based on nanoporous anodic alumina. We introduce different electrochemical approaches to modify the pore geometry during or after the fabrication processes. We will show how different nanoporous anodic alumina structures can be designed with particular photonic properties and how engineered porous anodic alumina nanotubes can be chemically modified and decorated with magnetic nanoparticles. Finally, we present different applications of nanoporous anodic alumina for optical sensing, drug delivery and cell culture.

(Invited) Factors Influencing the Performance of Vanadium Flow Batteries: Electrodes and Electrolytes

The electrochemical kinetics of the VII-VIII reaction on carbon electrodes is enhanced by anodic treatment and inhibited by cathodic treatment. In contrast, the kinetics of VIV-VV is inhibited by anodic treatment and enhanced by cathodic treatment. Rate constants are greater for VIV-VV than for VII-VIII under comparable conditions. The observed effects are attributed to oxygen-containing species on the surface of carbon electrodes and it is likely that enhancement of both VII-VIII and VIV-VV is due to the same (active) state of the electrode. Oxidation of this active state leads to inhibition of VIV-VV while reduction of the same active state leads to inhibition of VII-VIII. Using our standard methodology, we investigated the thermal stability of VFB catholytes. We showed that the induction time for precipitation of V2O5 decreases exponentially with increasing temperature or VV concentration but increases exponentially with increasing sulphate concentration. Arrhenius plots show two linear regimes, at 45–70°C and 30–45°C, respectively. We model this to estimate acceleration factors for testing of electrolyte stability over a range of test and use temperatures. Both arsenate and phosphate are effective additives for improving the thermal stability of VFB catholytes.

Evaluation of Bioabsorbable Mg-Mn Alloy with Anodic Oxidation Treatment.

Magnesium alloys as biodegradable materials have been examined that may replace bone screws and plates in recent studies. But the velocity control of magnesium alloy is very difficult. Until now, the magnesium alloys degrade very fast, thus it couldn't maintain the function in clinical field. Thus the purpose of this study is to evaluate the degradability of anodized magnesium alloy for control the velocity. For this experiment, a Mg-xMn (x = 0, 0.5, 1 wt%) binary alloy was cast in argon gas (99.99%) atmosphere. The specimens of the surface treatment group were anodized for 15 minutes at a voltage of 120 V at room temperature using calcium gluconate, sodium hexametaphosphate, and sodium hydroxide electrolyte. For the mechanical test, SEM, roughness test, hardness test were examined. The degradation test was conducted to measure the hydrogen gas formation volume. For biologic test, cell viability were tested. After anodic oxidation treatment, the surface showed the crater formation, the size of craters were about 200~300 nm. Among nonanodized group, the Mg-0.5Mn showed the highest Vickers hardness and cell viability. However for biodegradability test, Mg-1Mn showed the lowest the hydrogen gas formation. For anodic oxidation treatment, anodic oxidation treatment makes rougher surface, higher hardness, good cell response and lower degradation rate. Overall, anodized Mg-1Mn showed the possibility for clinical application in bone screw and bone plate.

Electrochemical Surface Treatment to Enhance Corrosion Resistance and Bioresistance of Medical-Grade Stainless Steels

The room-temperature eco-friendly electrochemical surface treatment of medical-grade stainless steels in ethaline, a eutectic mixture of choline chloride and ethylene glycol in a molar ratio of 1:2, is investigated in this work. High levels of brightness, smoothness and corrosion resistance of the surfaces of the stainless steels Mn AISI, AISI 316Ti, and AISI 304 can be achieved by using the technique of anodic treatment in ethaline. The surface smoothing of the steel samples due to the dissolution of defects and inhomogeneities, and the enrichment of the electropolished surfaces with chromium and nickel, resulted in increased corrosion resistance and bioresistance. The results of the experiments demonstrated that with anodic treatment in ethaline it is possible to decrease the amount of the Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans microorganisms on the surfaces of the steel samples by a factor of up to 75. Thus, the deep eutectic solvent ethaline is a highly promising medium for significantly improving corrosion resistance and bioresistance of medical-grade stainless steels by anodic treatment.

Surface Observation of Plasma Electrolytic Oxidation-Treated Ti-6Al-4V Alloy After 2-Step Nano-Mesh Formation.

The purpose of this study was to investigate the surface observation of PEO-treated Ti-6Al-4V alloy after 2-step nano-mesh formation was investigated by FE-SEM, EDS, and XRD. Anodic oxidation treatment was performed on the electrolyte containing 0.8 wt.% Na/F and 1M H₃PO₄ to form a nanotube structure on the Ti-6Al-4V alloy. After removing the nanotube layer, PEO-treatment was performed on the electrolyte containing Mg and Zn ions. After forming the nanotubes, the nanomesh surface was obtained by removing the layer, and the surface roughness increased with cycle number of nanotube formation. Also, as the number of nanotubes increased, the anatase peak increased.

Magnesium-doped Nanostructured Titanium Surface Modulates Macrophage-mediated Inflammatory Response for Ameliorative Osseointegration.

BackgroundNext generation of coating materials on the surface of implants is designed with a paradigm shift from an inert material to an osteoimmunomodulatory material. Regulating immune response to biomedical implants through influencing the polarization of macrophage has been proven to be an effective strategy.MethodsThrough anodization and hydrothermal treatment, magnesium ion incorporated TiO2 nanotube array (MgN) coating was fabricated on the surface of titanium and it is hypothesized that it has osteoimmunomodulatory properties. To verify this assumption, systematic studies were carried out by in vitro and in vivo experiments.ResultsMg ion release behavior results showed that MgN coating was successfully fabricated on the surface of titanium using anodization and hydrothermal technology. Scanning electron microscopy (SEM) images showed the morphology of the MgN coating on the titanium. The expression of inflammation-related genes (IL-6, IL-1β, TNF-α) was downregulated in MgN group compared with TiO2 nanotube (NT) and blank Ti groups, but anti-inflammatory genes (IL-10 and IL-1ra) were remarkably upregulated in the MgN group. The in vitro and in vivo results demonstrated that MgN coating influenced macrophage polarization toward the M2 phenotype compared with NT and blank-Ti groups, which enhanced osteogenic differentiation of rat bone mesenchymal stem cells rBMSCs in conditioned media (CM) generated by macrophages.ConclusionMgN coating on the titanium endowed the surface with immune-regulatory features and exerted an advantageous effect on osteogenesis, thereby providing excellent strategies for the surface modification of biomedical implants.

Protein adsorption, cell viability and corrosion properties of Ti6Al4V alloy treated by plasma oxidation and anodic oxidation

The hardness, wettability, and electrochemical properties of Ti6Al4V alloy surfaces treated with anodic oxidation and plasma oxidation as well as the viabilities of the different cell lines on the obtained surfaces were investigated. The anodic oxidation was performed for 10 min under 100 V potential, and it resulted in a 0.95 µm thick nanoporous anatase-TiO2 structure. On the other hand, plasma oxidation was carried out at 650°C for 1 h and resulted in a dense rutile-TiO2 structure with a thickness of 1.2 µm. While a hardness of HV0.025 823 and roughness of ∼220 nm were obtained by plasma oxidation, those obtained by anodic oxidation were HV0.025 512 and ∼130 nm, respectively. The anodic oxidation process created a more hydrophilic surface with a contact angle of 87.2°. Both oxidation processes produced similar properties in terms of corrosion behavior and showed better resistance than the as-received state in a certain range of potential. Moreover, the surface treatments led to no significant change in the protein adsorption levels, which indicates that the difference in viability between the osteoblast and fibroblast cells was not due to the difference in surface protein adsorption. Given all the factors, the surfaces obtained by anodic oxidation treatment revealed higher cell viability than those obtained by plasma oxidation (p = 0.05).

Corrosion Behaviors of Zn, Si, and Mn-Doped Hydroxyapatite Coatings Formed on the Ti-6Al-4V Alloy by Plasma Electrolytic Oxidation.

Ti alloy for implant materials is not good biocompatibility between metal implants and natural bone without surface modification. In order to improve the bone attachment ability, implant surface modification is required, and corrosion resistance is also important when a surface modified implant is inserted into the body. In this study, corrosion behaviors of anodic oxide film formed on Ti-6Al-4V alloy with concentration of Mn and Zn ions were studied using various experimental techniques. Ti-6Al-4V ELI disk were used as the substrate for PEO treatment. The sample was used a anodic electrode and PEO treatment was carried out by varying the content of each of the electrolytic solutions containing Zn, Mn, Si, Ca and P, using a Pt bar as a cathodic electrode. Pulsed DC power was used at 280 V for 3 min. For the corrosion behaviors of the specimens, the potentiodynamic polarization and AC impedance test were carried out in 0.9% NaCl solution. From the result of experiments, as Zn ion content increases, the number of pores and the pore size increase. As the Mn ion increases, the number of pores decreases, while the pore size increases. As the ions of Mn increase, the corrosion potential decreases. As Zn ion content increased, the polarization resistance increased.

Rechargeable Al-Metal Aqueous Battery Using NaMnHCF as a Cathode: Investigating the Role of Coated-Al Anode Treatments for Superior Battery Cycling Performance

Rechargeable Al-ion aqueous batteries (AIABs) are emerging contenders for massive battery systems due to economic, abundance, environmental, and safety advantages. However, the high capacity of met...

Incorporation of Sr2+ and Ag nanoparticles into TiO2 nanotubes to synergistically enhance osteogenic and antibacterial activities for bone repair

Osteogenic and antibacterial activities are two basic requirements for orthopedic implants. The present study mainly focused on the investigation of the osteoblast behaviors and antibacterial activities of Sr/Ag-incorporated titanium dioxide (TiO2) nanotube array (TNT) on the titanium surface. To this end, the Sr-incorporated TNT was firstly fabricated on the titanium surface by electrochemical anodization and hydrothermal treatment, and then Ag nanoparticles (AgNPs) were incorporated onto the nanotubes by reduction of the adsorbed Ag+ through ultraviolet (UV) irradiation. The TiO2 nanotubes had excellent hydrophilicity and Sr incorporation can further enhance the hydrophilicity; however, the AgNPs loading could slightly increase water contact angle. The release of Sr2+ can not only promote osteoblast adhesion, proliferation and mineralization, but also up-regulate the alkaline phosphatase (ALP) and osteocalcin (OCN) expression. The introduction of AgNPs on Sr-incorporated nanotubes did not significantly influence the osteoblast cell behaviors; however, it can effectively inhibit the adhesion and growth of Escherichia coli. Therefore, the method of the present study is expected to be suitable for surface modification of titanium surface to simultaneously enhance the osteo-bonding ability and antibacterial activities for bone repair.

Zr4+-Doped Anatase TiO2 Nanotube Array Electrode for Electrocatalytic Reduction of L-cystine

A Zr4+-doped anatase TiO2 nanotube array electrode was prepared using a process that included Ti anodizing, chemical immersion, and heat treatment. The compositions, microstructure, and electrochemical properties of the prepared electrodes were characterized. The results show that Zr4+ was successfully introduced into the TiO2 nanotube array electrodes. Because Zr4+ was doped into the crystal structure of the TiO2and replaced a part of Ti4+ to form more oxygen vacancies and Ti3+, the electrocatalytic activity of the prepared electrodes, for the reduction of L-cystine, was significantly improved.

Altered cortical gray matter volume and functional connectivity after transcutaneous spinal cord direct current stimulation in idiopathic restless legs syndrome

ObjectiveTo explore the neurophysiological mechanism of clinically effective transcutaneous spinal cord direct current stimulation (tsDCS) on idiopathic restless legs syndrome (RLS), structural magnetic resonance imaging (sMRI), and resting-state functional MRI (rs-fMRI) were applied to reveal the structural and functional changes in idiopathic RLS patients after tsDCS. MethodsThirty idiopathic RLS patients and 20 gender- and age-matched healthy controls (HC) were enrolled. All patients were randomly divided into anodal treatment group and sham treatment group and were treated with tsDCS for 2 weeks. The international RLS Rating Scale (IRLS-RS) and Pittsburgh Sleep Quality Index (PSQI) were used to evaluate the severity of RLS and sleep quality respectively. The sMRI and rs-fMRI data of anodal treatment group and HC were collected. Voxel-based morphology (VBM) and resting-state functional connectivity analysis were used to assess the change of cortical gray matter volume (GMV) and corresponding functional connectivity (FC) respectively in anodal treatment group after tsDCS treatment. ResultsSham treatment group showed no significant change in IRLS-RS and PSQI scores after tsDCS, while significant decrease scores were observed in anodal treatment group, and the improvement sustained up to 2 weeks. Anodal treatment group showed significant regional decrease of GMV in bilateral cuneus compared to the HC. After tsDCS treatment, the GMV in the bilateral cuneus and left ventral post central gyrus (PoCG_L) decreased significantly. The FC between bilateral cuneus and left primary visual cortex (V1_L), and between right cuneus (Cune_R) and right lingual gyrus (LG_R) increased significantly after tsDCS, whereas the FC between PoCG_L and supplementary motor area (SMA) decreased significantly. The changed FC between PoCG_L and SMA, between Cune_R and V1_L were correlated with the changed IRLS-RS. ConclusionDisturbance of sensorimotor network and visual processing network may be involved in the pathogenesis of RLS. tsDCS probably can regulate FC in the sensorimotor cortex and visual processing cortex to relieve the symptom of RLS. Continuous tsDCS may improve the symptoms of RLS patients for a long time. tsDCS probably could provide a potential non-pharmacologic treatment for idiopathic RLS patients.

20‐4: Study on the Effect of OLED Device Lifetime Improvement according to Hole Injection Barrier and p‐Dopants

In testing a special anode pretreatment technique to improve the lifetime of fluorescent blue devices, we found that the characteristics of two different blue devices with similar device lifetimes appeared to be significantly different after pretreatment. One device experienced a slight rise in drive voltage after pretreatment, but an increase in efficiency and lifetime, while a dramatic decrease in both. Accompanied by device measurement and analysis, it was found that the cause of lifetime degradation was the formation of a hole injection barrier, which resulted in the reduction of charge accumulation and recombination in the emitting layer. Therefore, it was confirmed that the increase of p‐type doping concentration can overcome the lifetime degradation phenomenon by increasing the hole and also increase the lifetime by lowering the barrier by additional mild plasma treatment of anode.

A scanning electrochemical microscopy characterization of the localized corrosion reactions occurring on nitinol in saline solution after anodic polarization

Scanning electrochemical microscopy (SECM) in a combined amperometric/potentiometric operation was used to characterize the electrochemical activity of nitinol, before and after anodic treatment, in 0.1 M NaCl solution. The SECM operation in the feedback mode showed that the nitinol surface was homogeneously passive after surface finishing and storage under ambient conditions, while heterogeneous surface characteristics occurred after application of anodic polarization, even for a limited time. That is, the development of anodic and cathodic sites has been detected due to the onset of localized corrosion processes on the metal surface. The evolution of hydrogen gas from localized sites was monitored using SECM in the substrate generation/tip collection mode (SG/TC), while SECM operated in potentiometric mode was used to map the pH distribution in the electrolyte volume adjacent to the nitinol surface. Local acidification was observed around anodic spots associated with the Ni2+ discharge, as well as alkalinization above the cathodic zones.

Pore structure control of anodized alumina film and sorption properties of water vapor on CaCl2-aluminum composites

Recently, increasing research attention has been given to the development of an absorber to enhance the coefficient of performance (COP) and the capacity of an adsorption heat pump by improving the sorbent in the sorption chamber or reactor. This study introduces the preparation method for an efficient adsorbent with a high thermal conductivity. Three types of host matrix aluminum composite sorbents were prepared through anodizing and pore widening treatment (PWT). This created an aluminum oxide film that was 92 μm thick with a mean pore diameter of 76 nm on an aluminum plate. To improve the sorption ability, the anodized aluminum was impregnated with calcium chloride. The sorption isotherm of the aluminum composite demonstrated its ability to uptake 7.5 mol-H2O/mol-CaCl2 water at a relative pressure of 0.33 at 30 °C. A numerical method was used to predict water sorption and temperature distribution in the aluminum composite layer via a heat and mass transfer model. The specific cooling power (SCP) was used to indicate the cooling performance of a sorption heat pump that employed the aluminum composite as laminate sorbent fins by varying the spacing between each fin.

Assisted reverse electrodialysis for CO2 electrochemical conversion and treatment of wastewater: A new approach towards more eco-friendly processes using salinity gradients

In this paper, the utilization of assisted reverse electrodialysis (A-RED), recently used for pre-desalination, is proposed as a general method to reduce the energy requirements of electrolysis processes and evaluated for two model processes: (i) the cathodic conversion of carbon dioxide to formic acid; (ii) the anodic treatment of water contaminated by organics. In A-RED, two solutions with different salt content and an external potential difference, applied in the direction of the natural salinity gradient, are both used to drive redox processes. It was shown, for the first time, that the cathodic conversion of CO2 to formic acid can be performed by both reverse electrodialysis (RED) and A-RED, saving electric energy with respect to electrolysis processes. A-RED allows to increase significantly the production of formic acid with respect to RED (after 4 h, 2 and 6.3 mM were produced for RED and A-RED with an additional external cell potential of 0.8 V, respectively, for a salinity ratio SR = 3300). For the anodic treatment of wastewater, A-RED allowed to accelerate the removal of organics and/or to use smaller salinity gradients with respect to RED (as an example, after 2 h with a SR of 4.4, an abatement of TOC of 55 and 92% was obtained with RED and A-RED with 1.5 V, respectively) and to save electrical energy with respect to electrolysis. A simplified economic analysis performed for the anodic treatment of the adopted synthetic wastewater has shown that A-RED presents the most appealing economic data with respect to both electrolysis and RED in most of investigated cases.

Removal mechanism of epoxy resin from CFRP composites triggered by water electrolysis gas generation

To promote recycling of carbon fiber reinforced plastics (CFRPs), we investigated the removal mechanism of resin by electrical treatment at high voltage. Using the pseudo in-situ observations, we found that resin removal was triggered by electrical treatment. Based on the observations and current dependency, the resin was removed by a mechanical approach that employed the oxygen gas generated from water electrolysis, i.e., the gas peeled the resin. Moreover, the cathodic treatment was unable to achieve the resin removal because of the high diffusion of hydrogen gas into the epoxy resin. During anodic treatment, CO, CO2, and oxygen gases were generated from the specimen, and damage to the carbon fiber (CF) was observed on the specimen after treatment for 180 min. The mechanism of the resin removal was governed by the resin peeling off from the CFRP composite, which was triggered by the oxygen gas generated from the water electrolysis. During electrical conduction, the peeling was initiated at the voids that were formed by the oxidation of the locally heated resin spots. At low resin content levels, the CF was subjected to damage due to the electrical conduction, which was accompanied by the application of a high voltage.

Electrochemical Descaling of Metal Oxides from Stainless Steel Using an Ionic Liquid-Acid Solution.

Oxide scales often formed on the surface of stainless steel, and it is of high interest to descale the surface oxide effectively and environment-friendly during steel smelting and engineering processing. It is generally done by treating the oxide layer under strong and harsh mixed acid (HNO3 + HF) conditions or in a strong molten salt (NaOH + NaNO3) environment at high temperatures, while the generation of very harmful and environmentally hazardous gases, such as NOx, is inevitable. A novel, simple, fast, and environment-friendly electrochemical method at ambient temperature is proposed in this research to remove the oxide scale from the stainless steel surface using an ionic liquid with a small amount of HCl. It was found that the optimized electrochemical anodization treatment in an ionic liquid environment could significantly improve the descaling efficiency at least 50 times faster than the simple passive and slow dissolution in a mixture of an ionic liquid and a concentrated acid.

Improvement the corrosion Behavior of Titanium by Nanotubular Oxide in a simulated saliva solution

The corrosion behavior of Titanium in a simulated saliva solution was improved by Nanotubular Oxide via electrochemical anodizing treatment using three electrodes cell potentiostat at 37°C. The anodization treatment was achieved in a non-aqueous electrolyte with the following composition: 200mL ethylene glycol containing 0.6g NH4F and 10 ml of deionized water and using different applied directed voltage at 10°C and constant time of anodizing (15 min.). The anodized titanium layer was examined using SEM, and AFM technique.The results showed that increasing applied voltage resulted in formation titanium oxide nanotubes with higher corrosion resistance (more positive value of the corrosion potential). The results revealed that good adhered well-ordered vertically aligned titania nanotubes with inner tube diameter of 82nm an mean length of 3microns could be obtained at 30VDC. Low corrosion current density (579 nA.cm-2) and corrosion potential equal to (-209 mV) were observed for untreated titanium metal while a dramatic fall down of the corrosion current was observed for nanotubes TiO2 (76 nA.cm-2) and more positive value of corrosion potential (-138 mV) was observed revealing good corrosion resistance of the improved titanium in saliva solutions.