Acid Anodizing Research Articles

Comparison of Ti–35Nb–7Zr–5Ta and Ti–6Al–4V hydrofluoric acid/magnesium-doped surfaces obtained by anodizing

ObjectivesDevelopment of a new generation of stable β alloy, free of aluminum or vanadium and with better biological and mechanical compatibility and evaluate the surface properties of Ti–6Al–4V and Ti–35Nb–7Zr–5Ta after anodization in hydrofluoric acid, followed by deposition of different electrolyte concentrations of magnesium particles by micro arc-oxidation treatment. MethodsDisks were anodized in hydrofluoric acid. After this first anodization, the specimens received the deposition of magnesium using different concentration (8.5% and 12.5%) and times (30s and 60s). The surface morphology was assessed using scanning electron microscopy, and the chemical composition was assessed using energy dispersive x ray spectroscopy. The surface free energy was measured from the contact angle, and the mean roughness was measured using a digital profilometer. ResultsAnodization in hydrofluoric acid provided the formation of nanotubes in both alloys, and the best concentration of magnesium considered was 8.5%, as it was the condition where the magnesium was incorporated without covering the morphology of the nanotubes. X-ray dispersive energy spectroscopy showed magnesium incorporation in all conditions. The average roughness was increased in the Ti–35Nb–7Zr–5Ta alloy. ConclusionsIt was concluded that anodizing could be used to deposit magnesium on the surfaces of Ti–6Al–4V and Ti–35Nb–7Zr–5Ta nanotubes, with better results obtained in samples with magnesium concentration in 8.5% and the process favored the roughness in the Ti–35Nb–7Zr–5Ta group.

The effect of carboxyl group position of pyrazinedicarboxylic acid on electrochemical performances in lithium ion batteries anode

Conjugate carbonyl compounds are considered to be one of the most promising electrode materials for the next generation of lithium ion batteries. However, most of the published researches focus on the electrochemical performances of conjugated carbonyl compounds, the researches on the structure-activity relationship of such materials are still not enough. In this work, we investigate the structure-activity relationship of pyrazinedicarboxylic acid (Pzdc) anode materials, and the results show that the lithium storage capability of 2, 3-Pzdc is much better than 2, 5-Pzdc and 2, 6-Pzdc. At 32 mA g−1, 2, 3-Pzdc is able to deliver a discharge capacity around 1200 mA h g−1, while 2, 5-Pzdc and 2, 6-Pzdc anodes only exhibit a capacity of 530 and 550 mA h g−1, respectively. Even at 32 A g−1, 2, 3-Pzdc still retains ca. 500 mA h g−1, and shows 1225 mA h g−1 after 400 cycles at 160 mA g−1 charge and 640 mA g−1 discharge. The combination of electrochemical and spectroscopic studies show that the good electrochemical performance of the 2, 3-Pzdc anode is because of the high lithium conductivity, the low resistance, the stable solid electrolyte interface film form on the electrode, as well as the rich lithium storage functional groups.

Impacts of electrokinetic isolation of phosphorus through pore water drainage on sediment phosphorus storage dynamics

Pore water is a crucial storage medium and a key source of sediment phosphorus. A novel equipment based on electrokinetic geosynthetics (EKGs) was used for isolating phosphorus from eutrophic lake sediments through pore water drainage. Three mutually independent indoor group experiments (A, B, and C) were conducted to investigate the effects of voltage gradient (0.00, 0.25, and 0.50 V/cm) on pore water drainage capacity, phosphorus removal performance, sediment physicochemical properties, and phosphorus storage dynamics. The average reduction in the sediment moisture and total phosphorus content was 2.5%, 4.3%, and 4.6% and 28.15, 75.95, and 112.65 mg/kg after 6 days of treatment for A, B and C, respectively. Efficient pore water drainage through gravity and electroosmotic flow and electromigration of phosphate were the main drivers of sediment-dissolved and mobilized phosphorus separation. A high voltage gradient facilitated the migration of pore water and the phosphorus in it. The maximal effluent total phosphorous (TP) concentration was up to 27.9 times that in the initial pore water samples, and negligible effluent TP was detected when the pore water pH was less than 2.5. The TP concentration was exponentially and linearly related to the pH and electronic conductivity of the electroosmotic flow, respectively. The migration of H+ within the sediment matrix promoted the liberation of metals bounded to phosphorus, particularly of Ca–P and Fe–P. Pore water drainage through an EKG resulted in Ex–P separation of up to 87.50% and a 13.84 mg/kg decrease in Ca–P and 125.35 mg/kg accumulation of low mobile Fe–P in the weak acid anode zone.

Effect of hydrothermal treatment on porous anodic alumina generated by one-step anodization

Abstract The effects of the hydrous oxide film obtained from the hydrothermal treatment of the electropolished aluminum sheet on the porous anodic alumina produced by the first step of anodization in oxalic acid were investigated. It is indicated that the dense barrier layer within the hydrous oxide film can bring about a nearly exponential decrease of the current as a function of time. As to the porous layer of the hydrous oxide film, namely the ‘cornflake’ structure onto the barrier layer, it can optimize the initially nucleated site of the nanoporous during the anodization, which is beneficial to the self-ordered array of the nanoporous generated on the PAA film. It is concluded that the hydrous oxide film produced by the hydrothermal treatment can facilitate the self-assembly of the porous anodic alumina even if the applied potential is 60 V in oxalic acid.

Interferometric colours produced by anodised aluminium diffraction grating

Highly ordered dimple arrays that give rise to bright structural colours with a rainbow distribution have been fabricated by means of etidronic acid anodising and subsequent selective oxide dissolution. High-purity aluminium samples were anodised at 270 V and 313 K and after removing the alumina porous film, highly ordered structures were obtained with two different cell diameters, namely 701 ± 43 and 655 ± 36 nm. These highly ordered near-subwavelength structures fabricated on the aluminium surface induced an optical effect for surface colorisation that could be predicted by interferometric equations. The generated angle-dependent colours were investigated. The mathematically predicted colours agree well with the reflected measured colours.

Photoluminescence from Anodic Aluminum Oxide Formed via Etidronic Acid Anodizing and Enhancing the Intensity

Photoluminescence from Anodic Aluminum Oxide Formed via Etidronic Acid Anodizing and Enhancing the Intensity

Optimization of preparation technology on fibre metal laminates (FMLs) for high-temperature applications

Fibre metal laminates based on titanium and carbon fibre reinforced polyimide (TCP-FML) are designed and manufactured to meet the requirements of high temperature applications. In this work, the preparation technology of the TCP-FML was optimized through the investigation of prepreg manufacture as well as surface treatment of titanium. Prepreg were manufactured using a solution dip method. The effects of step width, fibre tension and translational speed on the performance of prepreg were studied. Surface treatments were performed on titanium using sandblasting, chromic acid (CAA) anodization and NaTESi anodization methods. SEM observation and contact angle were used to analyze the surface characteristics of titanium. The effects of surface treatment on the interlaminar properties of titanium/polyimide were investigated by single-lap shear test and double cantilever beam (DCB) tests. This careful surface preparation, to ensure a good interfacial strength, is crucial for good mechanical properties.

Coating adhesion of a chromate-containing epoxy primer on Al2024-T3 surface processed by laser-interference

In this study, the coating adhesion test results are presented for a primer that was coated on laser-interference structured surfaces of as-received Al2024-T3 specimens, i.e., without employing any polishing, cleaning, or any other surface alteration techniques. All of the laser-interference processing was performed by splitting the primary beam of a Q-switched Nd:YAG pulsed nanosecond laser into two beams and focused them to the same spot. The specimens were spray painted with a chromate-containing epoxy primer, CA7233, compliant to MIL-PRF-23377 Type I Class C2 specification. The adhesion of primer on Al surface with different treatments was assessed using the ASTM D3359 X-cut and cross-hatch tests. It was found that the laser processed specimens meet the performance requirements in the coating adhesion specifications by having a higher or identical ranking for coating adhesion specimens than those prepared with current state-of-the-art chemical conversion or sulfuric acid anodizing. The rastering with either 4 mm/s or 6 mm/s with a laser fluence of 1.78 J/cm2 is recommended to attain acceptable coating adhesion, even higher than that with the anodizing surface treatment.These results indicate that laser-interference shows significant potential as a non-chemical surface preparation technique for these coatings.

Self-Organizing Anodization in Pure Molten Ortho-Phosphoric Acid: Nanoporous Niobium Oxide Layers

The anodic oxidation of niobium[1–4] is investigated in an electrolyte composed of pure, molten ortho-phosphoric acid, i.e. o-H3PO4.[5–7] In a range of applied potential of 2.5-60 V and for temperatures of 60-110°C, porous niobium oxide layers can be formed.Pore ordering and layer morphology depend on the anodization voltage, time and temperature.At 100°C and 5 V, vertically-oriented, defined amorphous nanochannels grow with an average diameter of 6-8 nm. Higher voltages (10-20 V) lead to a lower pore ordering and to a less defined morphology that resembles a “fish bone” structure. Interestingly, at 40-60 V and after a sufficiently long anodization time (≥ 30 min), we observe the formation of a partially crystalline Nb2O5 hierarchical structure. Such structure shows a bimodal pore size distribution, with some 100 nm wide main pores that branch out into ~ 10 nm sized nanochannels.We propose that high voltages (> 40 V) cause significant heating at the oxide/metal interface and a consequent partial crystallization of the anodic oxide. The main pore walls, partially crystalline and hence more stable in the anodizing environment, result from a gradual dissolution of the side nanochannels.[1] Q. Lu, T. Hashimoto, P. Skeldon, G. E. Thompson, H. Habazaki, K. Shimizu, Electrochem. Solid-State Lett. 2005, 8, B17–B20.[2] I. Sieber, H. Hildebrand, A. Friedrich, P. Schmuki, Electrochem. commun. 2005, 7, 97–100.[3] J. Choi, J. H. Lim, S. C. Lee, J. H. Chang, K. J. Kim, M. A. Cho, Electrochim. Acta 2006, 51, 5502–5507.[4] W. Wei, K. Lee, S. Shaw, P. Schmuki, Chem. Commun. 2012, 48, 4244.[5] M. Altomare, O. Pfoch, A. Tighineanu, R. Kirchgeorg, K. Lee, E. Selli, P. Schmuki, J. Am. Chem. Soc. 2015, 137, 5646–5649.[6] K. K. Upadhyay, M. Altomare, S. Eugénio, P. Schmuki, T. M. Silva, M. F. Montemor, Electrochim. Acta 2017, 232, 192–201.[7] K. K. Upadhyay, G. Cha, H. Hildebrand, P. Schmuki, T. M. Silva, M. F. Montemor, M. Altomare, Electrochim. Acta 2018, 281, 725–737.

Sr-containing micro/nano-hierarchical textured TiO2 nanotubes on 3D printing titanium

The design of biomimetic structures on the surface of titanium implants is critical to improve cell response and bone integration. In this work, Sr-incorporated micro/nano hierarchical structures coatings were fabricated on 3D printing titanium by acid etching, anodization, and hydrothermal treatment. Various characterizations were used to investigate the morphology, hydrophilicity, corrosion resistance, crystal phase, and chemical composition of coatings. Furthermore, we also investigated their in-vitro mineralization capacity upon soaking in simulated body fluid. The obtained coatings show not only excellent corrosion resistance (−0.32 V), high adhesion strength (10.51 N), and hydrophilicity (7.6°), but also superior apatite induction ability. These results suggest that Sr-containing micro/nano-hierarchical textured coatings exhibit potential applications in orthopedic implant materials.

Ultra-fast fabrication of porous alumina film with excellent wear and corrosion resistance via hard anodizing in etidronic acid

This paper describes a fast-fabrication strategy for hard-anodized film prepared on 6063T5 aluminum alloy in environmentally friendly etidronic acid (HEDP). The mild HEDP anodizing was first investigated at a temperature range of 15–45 °C, just under the burning current densities. The voltage curves and microstructures of the anodized film prepared in HEDP (Eti-film) indicate that 35 °C is the most appropriate temperature for the fast fabrication of Eti-film, in contrast to the micro-arc oxidation (MAO) coating and the seriously surface-corroded Eti-film prepared at 15 and 45 °C, respectively. Then, the HEDP hard anodizing without burning was successfully conducted via a gradient-increase-current approach, resulting in a high growth rate (~ 2.1 μm/min), low porosity (< 10%), thick barrier layer (~510 nm) and branched nanoholes structure of the hard anodized Eti-film. The Eti-films were systematically investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and a nanoindentation tester. In addition, the wear and corrosion resistance of the Eti-film and the hard sulfuric acid anodized film (Sul-film) were compared. The results indicate that the hardness of the Eti-film can reach ~ 11 GPa (~ 1000 HV0.01). The better wear resistance of the Eti-film as compared to the currently widely used Sul-film is attributed to the low porosity and less hydrated alumina content of the Eti-film. Moreover, the corrosion resistance of the Eti-film has been found to be 10 times higher than that of the Sul-film. In general, our results suggest a possibility of replacing the pollution-carrying anodizing methods currently used in the industry with the etidronic acid anodizing.

Effects of surface modification and graphene nanoplatelet reinforcement on adhesive joint of aluminium alloys

In this study, the combinative effects of surface treatments and the reinforcement of graphene nanoplatelets (GNPs) on the adhesive joint of aluminium alloy were investigated. Aluminium alloy plates were treated with acetone cleaning, grit blasting, chemical etching, and phosphoric acid anodisation (PAA) under various conditions. The effects of hydrothermal sealing of the anodised aluminium were also studied. Surface energies of the treated aluminium plates were determined using contact angle measurements. The samples were then bonded with epoxy or GNPs reinforced epoxy adhesives. The bonding strength of the aluminium joints was measured by single lap shear tests. The joint strength was significantly affected by both surface treatment and the reinforcement of GNPs. For grit blasted and PAA samples with hydrothermal sealing, the joint strength increased by 64% and 57% respectively due to the addition of 0.42 wt% of GNPs. Across all surface treatments, the highest average shear strength (17.6 MPa) was achieved for PAA samples with hydrothermal sealing and the addition of GNPs followed by PAA samples with no sealing and pure epoxy (17.0 MPa). Fractal surface images were analysed, and the correlation between epoxy infiltration behaviour, surface treatments and nano-reinforcement was critically discussed.

Durability of Metal-Composite Friction Spot Joints under Environmental Conditions.

The current paper investigates the durability of the single-lap shear aluminum-composite friction spot joints and their behavior under harsh accelerated aging as well as natural weathering conditions. Four aluminum surface pre-treatments were selected to be performed on the joints based on previous investigations; these were sandblasting (SB), conversion coating (CC), phosphoric acid anodizing (PAA), and PAA with a subsequent application of primer (PAA-P). Most of the pre-treated specimens retained approximately 90% of their initial as-joined strength after accelerated aging experiments. In the case of the PAA pre-treatment, the joint showed a lower retained strength of about 60%. This was explained based on the penetration of humidity into the fine pores of the PAA pre-treated aluminum, reducing the adhesion between the aluminum and composite. Moreover, friction spot joints produced with three selected surface pre-treatments were held under outside natural weathering conditions for one year. PAA-P surface pre-treated specimens demonstrated the best performance with a retained strength of more than 80% after one year. It is believed that tight adhesion and chemical bonding reduced the penetration of humidity at the interface between the joining parts.

Surface Reconstruction, Hydration, and Adhesion of Epoxy to the (0001) Surface of α-Berlinite: Insights from Density Functional Theory Calculations

Phosphoric acid anodization (PAA) is a candidate for replacement of toxic chromates during the surface treatment of aluminum prior to gluing in the aerospace industry. During PAA, a layer of AlPO4 ...

A study on Ti anodic pretreatment for improving the stability of electrodeposited IrO2 electrode

The anodization pretreatment, in hydrofluoric acid with different concentrations, was applied on titanium for improving the stability of electrodeposited IrO2/Ti electrodes. A developed plating bath was adopted to electrodeposit IrO2 on titanium substrates pretreated by three different pretreatment methods. The morphological characteristics, microstructure, electro-catalytic activities, and stability of electrodeposit IrO2 electrodes were observed and examined. In all cases, the hydrofluoric acid anodization improved the homogeneity and evenness of titanium substrates as well as the deposits. Among all samples, the electrodes with 1.0 wt% HF anodization exhibited the highest electro-catalytic activities and the ones with 0.5 wt% HF anodization exhibited the longest accelerate life time. The results indicate that anodization pretreatment in hydrofluoric acid has certain impacts on electrodeposited IrO2/Ti electrodes, although the effects depend on HF concentration. It might be suggested that a porous-structure was generated on titanium surface with hydrofluoric acid anodization, which may influence IrO2 electrodeposition, and thus the electro-catalytic activities and stability of such electrodes.

Bipolar-interface fuel cells – an underestimated membrane electrode assembly concept for PGM-free ORR catalysts

We present the first combination of a bipolar interface fuel cell with a commercial Fe–N/C catalyst as an alkaline cathode and a PGM-based, acidic anode, both separated by a proton exchange membrane (PEM).

Formation Mechanism of Strip Defects in Anodizing AA5252 Aluminium Alloy Sheets

Processed by sulfuric acid anodizing, several unexpected strip defects exhibited on the anodizing film of AA5252 aluminium alloy sheets. Their formation mechanism was studied in detail. The normal zone and strip zone were compared, with respect to surface brightness, porosity of anodizing film, and microstructures of the corresponding aluminium substrate tested by spectroscopic colorimeter and SEM, and SEM-EBSD. Results showed that the brightness of strip zone was lower than that of normal zone. Additionally, compared with normal zone, the porosity of anodizing film was higher, and cubic grains fewer, which located in the corresponding surface layer of aluminium substrate in strip zone. In order to further clarify the effect of grain orientation on the brightness of anodizing film, single crystal aluminium sheet with (100), (110) or (111) orientation was anodized. Results showed that the anodized (100) oriented specimen, i.e., cubic grain was brighter, whose anodizing film had lower porosity, compared with (110) and (111) oriented ones. Therefore, the formation mechanism of strip defects was proposed as uneven distribution of cubic grains. The zones with fewer cubic orientated grains were darker, and were visible as strip defects after anodizing.

Effects of surface pre-treatment and adhesive quantity on interface characteristics of fiber metal laminates

ABSTRACT Fiber metal laminates (FMLs) are hybrid materials consisting of metals and fiber-reinforced composite materials. The characteristics of interfaces between metal layers and layers of composites directly determine the damage tolerance and impact resistance of FMLs. In this study, the effects of surface pre-treatment and adhesive quantity on the interface of FMLs were investigated. Aluminum substrates were treated with sandpaper and anodizing. The treated surface structure and joint shear strength were evaluated to analyze the bonding interface quality. The results show that the surface roughness, structure and thickness of the anodized films affect the interface characteristics and adhesion strength. A porous oxide layer was formed on the substrate surface after anodization, resulting in a better wetting surface than that of sanded. Moreover, statistical analysis of the surface structures reveals that the shear strength of phosphoric acid anodizing treatment was higher than other anodizing. With the increase in adhesive layers, the lap shear strength was markedly improved at the beginning but slowly increased thereafter. From the results, the surface pre-treatment and adhesive quantity could be optimized to improve the manufacturing process of FMLs.

The effect of different carboxylic acids on the sulfuric acid anodizing of AA2024

Porous anodic oxides on AA2024-T3, grown in Cr(VI)-free mixtures of H2SO4 with carboxylic acids (malic, tartaric, oxalic, malonic, citric) under identical experimental conditions were comparatively studied. The corrosion resistance determined by pit initiation times in 0. 1 M NaCl is improved by the addition of malic, tartaric, and citric acid and impaired by malonic and oxalic acid. It is shown that the current efficiency of oxide formation can be obtained from the ∂Ecell/∂t value verified during barrier layer formation. The ranking of the corrosion performance can be deduced from electrochemical parameters of anodic oxide formation, morphology, structure, and composition of the oxide films. Beneficial for the corrosion resistance are higher voltage slopes ∂Ecell/∂t during barrier layer formation, which also indicates higher formation efficiency, as well as smaller flaws, denser oxides, lower OH− and S-content, as well as higher Cu content of the anodic oxide.

The effects of pore widening and calcination on anodized aluminum oxide prepared from Al6082

In this study, semi-organized anodized aluminum oxide (AAO) is prepared by two-step anodization in oxalic acid using a low-purity aluminum (Al) alloy (Al6082) as the source material. Obtaining ideally ordered AAO layers from Al alloys is confounded by the presence of impurities and requires specialized post-anodization treatment. Here, a process is proposed for obtaining an AAO layer with a semi-ordered pore arrangement by means of calcination and pore-widening procedures. Calcination temperatures of 400–600 °C and pore–widening times of 15–120 min were explored. It was found that calcination improved the pore order of AAO layers from disordered to semi-ordered (defined as being near ideally ordered—one pore surrounded by six neighboring pores). In addition, it was found that calcination at 600 °C resulted in suitable pore widening of the AAO layer. The morphology of the AAO layers was characterized using scanning electron microscopy, which was applied to determine pore diameter, inter-pore distance, pore density, and AAO layer thickness. We found that calcinated and pore-widened AAO layers with pore diameters of 48.7 nm, inter-pore distances of 80.6 nm, and pore densities of 178 pores/μm2 could be prepared. The AAO preparation method proposed here is an economically attractive process suitable for the preparation of AAO layers due to the utilization of an inexpensive Al source.