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Background : Endotension is one of the detrimental complications after endovascular aneurysm repair (EVAR) and surgical management has been considered as standard of care. However, there is a paucity of data regarding the findings and outcomes of such surgical intervention. The aim of this study was to investigate intraoperative findings and outcomes of surgical treatment for endotension after EVAR. Methods : Between January 2005 and October 2018, of the 708 patients who underwent EVAR for aneurysm aortic aneurysm; 12 patients (mean age of 76.1; range 66–88) who underwent open repair for endotension were retrospectively analyzed. The anatomical characteristics of the aorta and surgical findings were reviewed. The rates of early and late procedural complications, and overall mortality were evaluated. Results : The median interval between the EVAR and surgical conversion was 45.9 months (range 17.1–46.9). Three of the twelve patients underwent emergency surgery due to aneurysm rupture. The median aneurysm sac size, the proximal neck diameter, and the proximal neck length before EVAR were 64 mm, 23.5 mm, and 30.5 mm, respectively, that changed before open repair to 93.5 mm (p = .02), 25 mm (p = .011), and 23 mm (p = .003), respectively. In four of the twelve patients, radiographically undetected endoleak was identified during surgery to be Type Ia, Ib, II, and III, respectively. The rates of early and late procedural complications, and overall mortality were 8.3%, 8.3% and 8.3%, respectively. Conclusions : Patients with endotension have a risk of delayed endoleak and aneurysm rupture; secondary intervention should be performed in such cases to prevent fatal complications. Surgical treatment appears to be a curative treatment for endotension with favorable outcomes. In addition, the possibility of an undetected endoleak should be considered as a potential cause of endotension.

Background There have been conflicting outcomes regarding the use of lidocaine to reduce pain after uterine artery embolization (UAE). Purpose To investigate the efficacy of intra-arterial lidocaine injection for pain and inflammatory response control within 24 h of UAE for symptomatic uterine fibroids. Material and Methods Of 1530 patients who underwent UAE for uterine fibroids in 2007–2021, 5 mL of 1% lidocaine was injected into each uterine artery immediately after UAE in 23 patients. A disease-matched control group (n = 23) who did not receive intra-arterial lidocaine was generated from the same registry. The pain score, white blood cell (WBC) count, C-reactive protein (CRP), neutrophil/lymphocyte ratio (NLR), and fentanyl consumption were compared before and after UAE. Complete infarction of the dominant fibroid was assessed using magnetic resonance imaging. Results Significantly lower WBC count, CRP level, and NLR were noted 24 h after UAE in the lidocaine group. No statistically significant difference was noted in the pain score between groups at 0–24 h. The cumulative fentanyl dose administered during the first 24 h after UAE was not significantly different. After embolization, fibroid-related symptoms resolved in all patients. No significant difference was observed in the rate of complete infarction of the dominant fibroid. Conclusion Lidocaine administration immediately after UAE resulted in a significant reduction in the inflammatory response. However, such a difference in the inflammatory reaction did not contribute to significant reductions in pain scores or fentanyl consumption.

To compare the Celect and Denali filters in terms of complex filter retrieval and indwelling complications after a 2-month indwelling time. In this prospective, randomized trial, 153 subjects were assessed for eligibility between May 2016 and July 2018. A total of 136 participants were randomly assigned to receive either Celect (n = 68) or Denali (n = 68) filter placement in the infrarenal inferior vena cava. Tilt angles at placement and retrieval and rates of overall filter retrieval, indwelling complication, and complex retrieval were compared. Of 136 participants (mean age, 62 ± 12.8 years, 55 male), 24 (17.6%) were lost to follow-up. The mean indwelling time of filter was 60.4 ± 7 days and there was no significant difference in the baseline characteristics between the two groups. Filter retrieval was successful in all participants (112/112, 100%). Significantly higher rates of filter tilt > 15° (n = 8) and strut penetration (n = 14) were found with the Celect filter than with the Denali filter (1 significant tilt and 1 penetration) (P = 0.033 and 0.001, respectively). No filter fractures were observed and there was no significant difference in tip embedment, filter fracture, filter migration, or mean fluoroscopy times. There were 3 cases of complex retrieval (1 for Denali vs. 2 for Celect, P = 0.500), for which the loop-snare technique was used. Denali filters demonstrated significantly lower rates of tilt angle > 15° and strut penetration. However, there was no significant difference in the complex filter retrieval rate between the Celect and Denali filters.

Tribological behaviors of the plasma electrolytic oxidation (PEO)-treated Al1050 alloy surface without and with Ni-P deposits was examined by analyzing of the width of abrasion groove, weight loss, friction coefficient and composition at the wear track after a 100 m ball-on-disc test. The surface color, surface and cross-sectional morphologies and surface roughness (Ra) were also investigated to explain different wear behaviors of PEO films without and with Ni-P deposit. After the 100 m ball-on-disc test, a circular abrasion groove with relatively large width and shallow depth was formed when Ni-P particles cover the top surface of PEO films, but a relatively narrow and deep circular abrasion groove was formed on the Ni-P layer-covered PEO film surface. Iron was only detected at the wear track of 5 and 10 μm PEO films without Ni-P deposit, suggesting that the steel ball is worn out by the PEO films but not by the Ni-P deposit. An extremely large amount of weight loss was obtained from the Ni-P layer-covered PEO film surface, which could be related to the high density and low hardness of the Ni-P layer.

Background Signal intensity (SI) of predominant fibroid (F1) on T2-weighted (T2W) images is useful for predicting the volume reduction response after gonadotropin-releasing hormone (GnRH)-agonist treatment. Few studies have been published regarding when and how to use GnRH agonist before UAE. Purpose To investigate magnetic resonance imaging (MRI) prediction of volume reduction rate (VRR) of large fibroids after GnRH-agonist treatment before uterine artery embolization (UAE) as well as the efficacy of UAE based on MRI. Material and Methods Data from 30 patients with a large fibroid and MRI results both before and after GnRH-agonist treatment were retrospectively analyzed. Indications for GnRH-agonist treatment are fibroids with a maximum diameter ≥10 cm or pedunculated submucosal fibroids ≥8 cm. GnRH agonist (3.75 mg leuprolide acetate) was administered subcutaneously once per month 2–6 times. SI of F1 on T2W imaging was measured: the SI was referenced to the SI of the rectus abdominis muscle (F/R). Results Mean maximum fibroid diameter was 11.1 ± 1.9 cm (range = 8.0–15.5 cm). Mean number of GnRH-agonist injections before UAE was 2.8 (range = 2–6). For predicting VRR ≥50% and Conclusion SI of F1 on T2W imaging is useful for predicting the volume reduction response after GnRH-agonist treatment. After GnRH-agonist treatment for large fibroids, UAE is effective to achieve complete infarction of fibroids.

This study investigated the corrosion protection by electrodeposited copper layer on AZ31 Mg alloy with and without additional silver layer. The single copper layer electrodeposited on AZ31 from copper pyrophosphate bath exhibited nodular structure and crevices between the nodules which resulted in the rapid initiation of pitting corrosion. Employing an additional electrodeposited silver layer onto the copper deposited AZ31 alloy decreased the number of imperfections and changed structure of electrodeposited copper from nodular to fine particle type resulting in improved corrosion resistance. This study further revealed that triple-layer coating of Cu/Ag/Cu exhibited the most efficient corrosion protection of AZ31 Mg alloy.

Magnesium phosphate conversion coating (MPCC) was fabricated on AZ31 magnesium alloy for corrosion protection by immersion treatment in a simple MPCC solution containing Mg 2+ and PO 3− 4 ions. The MPCC on AZ31 Mg alloy showed micro-cracks structure and a uniform thickness with the thickness of about 2.5 µm after 20 min of phosphating treatment. The composition analyzed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed that the coating consisted of magnesium phosphate and magnesium hydroxide/oxide compounds. The MPCC showed a significant protective effect on AZ31 Mg alloy. The corrosion current of MPCC was reduced to about 3% of that of the uncoated surface and the time for the deterioration process during immersion in 0.5 mol/L NaCl solution improved from about 10 min to about 24 h.

In this work, electrophoretic paint (E-paint) was deposited on AZ31 Mg alloy after four different surface pretreatments: knife abrading, SiC paper abrading, deionized (DI) water immersion and NaOH immersion. The deposition process of E-paint was studied by analyses of voltage-time and current-time curves, amount of deposited paint, current efficiency and surface oxide film resistance and the adhesion of E-paint was examined by tape test before and after immersion in DI water for 500 h at 40℃. It was found that the induction time for the deposition, the amount of deposited paint and the current efficiency are inversely proportional to the resistances of surface films prepared by different surface pretreatment methods. The electrophoretic painting showed longer inductance time, larger amount of deposited paint and higher current efficiency on the highly conducting surfaces, such as knife-abraded and SiC-abraded surfaces than on the less conducting surfaces, such as DI water-immersed and NaOH-immersed samples. Excellent adhesion was observed on the E-paintings deposited onto knife-abraded and SiC-abraded AZ31 Mg alloy samples.

This work demonstrates arc generation and anodic film formation behaviors on Al1050 alloy during PEO (plasma electrolytic oxidation) treatment under a constant direct current in an alkaline electrolyte containing silicate, carbonate and borate ions. Only one big arc more than 2 mm diameter was generated first at the edges and it was moving on the fresh surface or staying occasionally at the edges, resulting in the local burning due to generation of an extremely big orange colored arc at the edges. Central region of the flat surface was not fully covered with PEO films even after sufficiently long treatment time because of the local burning problem. The anodic oxides formed on the flat surface by arcing once were found to consist of a number of small oxide nodules with spherical shape of 3~6 μm size and irregular shapes of about 5 ~10 μm width and 10~20 μm length. The anodic oxide nodules showed uniform thickness of about 3 μm and rounded edges. These experimental results suggest that one big arc observed on the specimen surface under the application of a constant direct current is composed of a number of small micro-arcs less than 20 μm size.

This study investigated cerium- and phosphate-based sealing treatments of PEO coated AZ31 Mg alloy samples in view of their characteristics and corrosion resistance in 0.5 M NaCl solution. Potentiodynamic polarization experiments and immersion tests in NaCl solution showed that corrosion resistance of PEO coated AZ31 was increased by the sealing treatment in cerium or phosphate solution. The combination of two sealing treatments, first in the cerium and second in the phosphate solution, was found to significantly increase the corrosion resistance of PEO coated AZ31. The best corrosion resistance was obtained for a sample with sealing treatment for 20 min in the cerium followed by 20 min in the phosphate solution.

In this study, the adhesion and corrosion resistance of electrophoretic paint (E-paint) were studied on AZ31 Mg alloy pretreated in cerium conversion coating (CeCC) solutions with and without addition of ethanol. It was found that the addition of ethanol to CeCC solution can decrease the formation of Mg(OH) 2 /MgO and increase the formation of nano-crystalline cerium oxides on AZ31. The E-paint on AZ31 pretreated in Ce-water-ethanol solution showed strong adhesion with no detachment after water immersion test for 500 h at 40 °C, and no blisters were observed on the surface and scratched lines after 1000 h salt-spray test. In contrast, the E-paint on AZ31 pretreated in Ce-water solution showed large blisters and weak adhesion with some flakes detachment along the intersections of cuts. Moreover, the E-paint on AZ31 pretreated in Ce-water solution showed that blisters are formed adjacent to the scratched lines after 500 h salt-spray test.

Electrophoretic painting (E-paint) was prepared on AZ31 Mg alloy samples pretreated in cerium conversion coating (CeCC) solutions with various ratios of ethanol and water mixture and its characteristics, adhesion and corrosion resistance were investigated. It was found that CeCC formed on AZ31 Mg alloy in a CeCC solution without ethanol was partly cracked structure and mainly consisted of Mg(OH)2/MgO, which exhibited weak adhesion with E-painting layer after water immersion test, and low corrosion resistance, as indicated by rapid formation of blisters and paint delamination during salt spray test. The addition of ethanol promoted the growth of a fine nano-crystalline CeO2 layer over the entire substrate surface. The E-paint on AZ31 pretreated in the CeCC solutions with addition of ethanol showed also improved corrosion resistance, as represented by the delayed time for paint delamination and blister formation. The E-paint layers on the CeCC layers formed in solutions containing 50–80 vol% ethanol showed stronger adhesion and better corrosion resistance than those formed on the samples treated in a non-ethanol containing CeCC solution.

This paper reports three different anodic oxidation behaviors of AZ31 Mg alloy in NaOH solutions, depending on the applied current density and concentration of NaOH between 0.1 M and 0.6 M. When applied current density is lower than about 30 mA/cm², dark anodic film was formed with a very low film formation voltage of less than 6 V and it was found to grow with anodizing time. If applied current density is higher than a critical value about 30 mA/cm², bright metallic surface appearance with small number of pits and/or trenches was obtained. The formation of the pits or trenches was attributed to the result of repeated formation and detachment of plasma electrolytic oxidation (PEO) films at the same site or neighboring places, as strongly supported by repeated micro-arc generations at the same surface site of the specimen during the anodic oxidation process. When applied current density exceeds about 80 mA/cm² in 0.6 M NaOH solution, micro-arcs were generated uniformly over the entire surface, resulting in grey surface appearance and the formation of PEO films with cracks and pores. Based on the experimental results obtained in this work, it is concluded that dark anodic films and grey colored PEO films can be formed on the AZ31 Mg alloy surface in NaOH solution if the applied current density is controlled to be lower than a critical value and if the applied current density and NaOH concentration are controlled to exceed critical values of about 80 mA/cm² and 0.6 M, respectively.

This article reports improved corrosion resistance and adhesion of electro-paint (E-paint) with fluoride conversion coating (FCC) on AZ31 Mg alloy for the first time. These improvements were observed in comparison to chemically polished samples with no chemical conversion coating and samples with cerium conversion coatings (CeCC). FCCs were prepared in a hydrofluoric acid (HF) solution for four different times; 10, 30, 60, and 120 s. The colour of the samples changed from light gold to brown with increasing immersion time, indicating the formation of thicker FCC coatings with increasing immersion time. The adhesion of the E-paint on FCC-coated AZ31 Mg alloy was tested after 500 h of immersion in deionized (DI) water. Salt spray test (SST) results revealed delamination of E-paint on the chemically polished sample, severe blistering on the samples with CeCC, but no delamination and no blistering on the samples with FCC.

In this work, effect of zincate treatment of AZ91 Mg alloy on the following electrodeposition of copper was examined in a non-cyanide bath containing pyrophosphate ions in view of surface morphology and adhesion of the electrodeposited copper layer. Without zincate treatment, the electrodeposited copper layer showed very porous structure and poor adhesion. On the other hand, the copper layer electrodeposited on the zincate-treated surface showed dense structure and good adhesion. The dissolution rate of AZ91 Mg alloy after the zincate treatment appeared to decrease about 40 times in the copper pyrophosphate bath, as compared to that of the surface without zincate treatment. The porous morphology and poor adhesion of a copper layer on the AZ91 Mg alloy surface without zincate treatment were attributed to small number of nucleation sites of copper because of rapid dissolution of the magnesium substrate in the pyrophosphate bath. Based on the experimental results, it is concluded that the zincate treatment to form a conducting and protecting layer on the AZ91 Mg alloy surface is essential for successful electrodeposition of a copper layer on AZ91 Mg alloy with good adhesion and dense structure in the copper pyrophosphate bath.

In this work, anodic oxidation behavior of AZ31 Mg alloy was studied as a function of Na₂CO₃ concentration in electrolyte by voltage-time curves and observation of surface appearances and morphologies after the anodic treatments, using optical microscopy and confocal scanning laser microscopy (CSLM). The voltage-time curves of AZ31 Mg alloy surface and surface appearances after the anodic treatments showed three different regions with Na₂CO₃ concentration : region I, below 0.2 M Na₂CO₃ where shiny surface with a number of small size pits; region II, between 0.4 M and 0.6 M Na₂CO₃ where dark surface with relatively low number of large size burned or dark spots; region III, more than 0.8 M Na₂CO₃ where bright surface with or without large size dark spots were obtained. The anodically treated AZ31 Mg alloy surface became significantly brightened with increasing Na₂CO₃ concentration from 0.5 M to 0.8 M which was attribute to the formation of denser and smoother surface films. Pits and porous protruding reaction products were found at relatively large size and small size spots, respectively, on the AZ31 Mg alloy surface in low concentration of Na₂CO₃ less than 0.2 M. The formation of pits is attributed to the result of repetition of the formation and detachment of porous anodic reaction products. Based on the experimental results obtained in this work, it is concluded that more uniform, denser and smoother surface of AZ31 Mg alloy could be obtained at more than 0.8 M Na₂CO₃ concentration if there is no other oxide forming agent.

Copper electrodeposition on AZ91 Mg alloy was studied in views of preferential deposition on α- or β-phases and how to achieve uniform deposition over the entire surface on α- and β-phases in a cyanide solution. The inhomogeneous microstructure of AZ91 Mg alloy, particularly α- and β-phases, was found to result in non-uniform deposition of zincate layer, preferential deposition of zincate on β-phases, which leads to non-uniform growth of copper layer during the following electrodeposition process. The preferential depositions of zincate can be attributed to higher cathodic polarizations on the β-phases. Pin-hole defects in the copper electrodeposit were observed at the center of large size β-phase particles which is ascribed to gas bubbles formed at the β-phases. The activation of AZ91 Mg alloy in hydrofluoric acid solution was used to obtain uniform growth of zincate layer on both the α- and β-phases. By choosing an optimum activation time, a uniform zincate layer was obtained on the AZ91 Mg alloy surface and thereby uniform growth of copper was obtained in a cyanide copper electroplating solution.

This article reports a new chemical bath for preparing a mirror-like surface of AZ31 Mg alloy. In order to find an appropriate chemical polishing solution, four different acidic solutions of sulphuric acid, nitric acid, acetic acid and a specially designed mixture of nitric acid and acetic acid were investigated in view of the changes in surface appearance, roughness and dissolution rate of AZ31 Mg alloy. The surface scales on AZ31 Mg alloy were readily removed by all the acidic solutions, but a reflective surface was produced only by etching in the specially designed solution, and only after a specific etching time. The surface roughness increased with etching time in sulphuric acid, nitric acid, and acetic acid, but it lowered after a specific etching time in the specially designed mixture of nitric acid and acetic acid. Dissolution rate of the alloy in the specially designed mixture of nitric acid and acetic acid appeared to be more than twice than that in separate nitric acid or acetic acid. In this work, we recommend the mirror-like surface of AZ31 Mg alloy obtained by polishing for an optimum time in a mixture of nitric acid and acetic acid for following surface finishings, chemical conversion coating, electroplating, electrophoretic painting and anodizing treatment.

A hybrid propulsion system composed of a homemade Polymer electrolyte fuel cell (PEFC) with a Lithium polymer (LiPo) battery in parallel connection was developed for Unmanned aerial vehicles (UAVs). The characteristics and performance of the system were evaluated considering its dynamic load responding capability and energy efficiency. A homemade PEFC stack composed of 36-unit cells and Balance of plant (BOP) was used to construct the fuel cell system directly connected to the propulsion system. Ten cells of a 3300-mAh 40C LiPo battery were combined with the PEFC system in parallel, and the LiPo battery was only switched on when high power was required for takeoff, acceleration and landing. The independent use of the homemade PEFC system and battery for the UAV showed a good load responding capability and a high fuel cell system efficiency of approximately 45%, which was obtained during cruising. The parasitic loss and the amount of unreacted hydrogen gas discharged outside of PEFC were nearly 3.91% and 0.89%, respectively. Results of the field test flights confirmed that the hybrid propulsion system based on the parallel connection of a PEFC system and a battery power is extremely effective in operating a UAV.

In this study, electrophoretic paint (E-paint) was deposited on the knife-abraded surface of AZ31 magnesium alloy (AZ31), and its adhesion and corrosion resistance were examined by tape peel-test and salt spray test, respectively. E-paint started to deposit on AZ31 Mg alloy after an inductance time and pores were found in the E-paint layer which is ascribed to hydrogen bubbles generated on the surface during the painting process. The pores disappeared after curing for 15 min at 160℃. The E-paint on AZ31 exhibited good adhesion after immersion in deionized water for 500 h at 40℃. The E-paint sample without scratch showed no corrosion after 1500 h of salt spray test. However, on the scratched sample, blisters were visible adjacent to the scratched sites after 500 h of salt spray test.

The structure of plasma electrolytic oxidation (PEO) coatings was investigated as a function of NaOH concentration in 0.06 M + 0.06 M solution by using SEM and epoxy replica method. The PEO film was formed on AZ31 Mg alloy by the application of anodic pulse current with 0.2 ms width and its formation behavior was studied by voltage-time curves during the formation of PEO films. It was found that the addition of NaOH into and containing aqueous solution causes a decrease in the PEO film formation voltage, suggesting that dielectric breakdown of the PEO becomes easier with increasing ion concentration in the solution. With increasing ion concentration, thickness of the PEO film increased and surface roughness decreased. The size of pores formed in the PEO layer became smaller and the number of cracks in the PEO layer increased with increasing ion concentration. Based on the experimental results obtained in the work, it is suggested that ions in the solution can contribute not only to the dielectric breakdown but also to the formation of PEO films in the presence of and ions in the solution.

This review deals with one of the surface modification techniques, chemical conversion coating and particularly cerium-based conversion coatings (CeCC) as a promising substitute for chromium and phosphate conversion coating on magnesium and its alloys. The CeCCs are commonly considered environmentally friendly. The effects of surface preparation, coating thickness, bath composition, and e-paint on the corrosion behavior of CeCCs have been studied on the AZ31 magnesium alloy. This review also correlates the coating microstructural, morphological, and chemical characteristics with the processing parameters and corrosion protection. Results showed that the as-deposited coating system consists of a three layer structure (1) a nanocrystalline MgO transition layer in contact with the Mg substrate, (2) a nanocrystalline CeCC layer, and (3) an outer amorphous CeCC layer. The nanocrystalline CeCC layer thickness is a function of immersion time and cerium salt used. The overall corrosion protection was crucially dependent on the presence of coating defects. The corrosion resistance of AZ31 magnesium alloy was better for thinner CeCCs, which can be explained by the presence of fewer and smaller cracks. On the other hand, maximum corrosion protection was achieved when AZ31 magnesium samples with thin CeCCs are e-painted. The e-paint layer further restricts and hinders the movement of chloride and other aggressive ions present in the environment from reaching the magnesium surface.

Electrophoretic paint (E-paint) was investigated on four different magnesium substrates: as-extruded AZ61 (AZ61), heat-treated AZ61 (AZ61-H), as-extruded TZ61 (TZ61) and heat-treated TZ61 (TZ61-H), to elucidate the effect of heat treatment and alloying elements on the deposition and characterization of E-paint. It was found that, a rapid increase of voltage, indicating the deposition of E-paint, was observed after an induction time of 0.39 min for AZ61-H, 0.43 min for AZ61, 0.51 min for TZ61-H and 0.58 min for TZ61. The amount of E-paint deposited on the four different samples was approximately similar, but the electrical charge used for the deposition process on the heat-treated samples was smaller than that on the as-extruded samples. Current efficiencies of E-painting on AZ samples (AZ61 and AZ61-H) were higher than those of TZ samples (TZ61 and TZ61-H), and the current efficiencies on the heat-treated samples were higher than those on as-extruded samples. All E-paintings on the four different magnesium substrates had an excellent adhesion without showing any detachment by tape peel test. After immersion test in deionized water (DI water) for 500 h at 40 °C, however, many large blisters were formed on the surface of AZ samples, and none or small blisters were observed on TZ samples. Salt spray test (SST) results showed that blisters were formed adjacent to the scratches on the E-painted AZ samples, while they were formed at the intact areas of E-painted TZ samples. The E-paints on heat-treated samples showed much better corrosion resistance than those on as-extruded samples.

Various imperfections can be formed in the anodic oxide films on aluminium alloys because of second-phase particles and they affect corrosion resistance and surface hardness of aluminium alloys. In this work, ink-impregnation method was newly employed to observe imperfections in the anodic films on AA2024 and to measure surface hardness of the anodic oxide films with different imperfections. The ink-impregnation allows clear observation of not only the imperfections within the anodic oxide films but also an indentation mark on the oxide film surface. Two different imperfections of black defects and grey defects were found in the anodic oxide films formed on AA2024 in 20% sulphuric acid solution and the surface hardness was dependent on the type, size and density of defects. Large size black defects showed the lowest hardness of 60 ~ 100 Hv. A little bit higher hardness of 100 ~ 140 Hv was measured on the large size grey defect. More increased hardness of 140 ~ 170 Hv was observed on the oxide surface region with mall size black and/or grey defects. The highest hardness of 170 ~190 Hv was obtained from the oxide surface without defects. Distortion of the pyramidal indentation marks were observed only in the regions with a large size black and grey defects.

A blade-abrading method was newly developed for the preparation of clean Mg alloy surface and reported for the first time in detail in this paper. The blade-abrading method includes abrading of the Mg alloy surface with a sharp blade or knife to remove the surface oxide and contaminants on the skin of Mg alloys mechanically, thereby providing very clean surface of Mg alloys. The clean surface prepared by the blade-abrading method in the air was found to be covered with thin and dense air-formed oxide films. Based on the experimental results obtained in this work, it is concluded that the newly developed blade-abrading technique is a very simple and useful pretreatment method which can provide clean and well-defined surface for the following surface treatments.

The present study reports the system configurations of a self-operated Polymer electrolyte fuel cell (PEFC) that is specially designed for dead-end operation of both pure hydrogen and oxygen gas lines, including its operation features and durability. The PEFC stack with 16 unit cells was constructed using homemade membrane electrode assemblies with 300 cm2 of apparent active area and bipolar plates. A self-operated PEFC system was developed using a homemade PEFC stack, balance of plant, and electric control unit for automatic fuel cell system operation. Performance parameters of the self-operated PEFC system, including fuel utilization, parasitic loss, released heat, purge loss, and efficiency of the PEMFC stack and system were evaluated during the automatic operation of the PEFC system. A Daily start-and-stop (DSS) test was also performed for one month to check the durability of the self-operated PEFC system. Electric efficiencies of the PEFC stack and system are approximately 60% and 49%, respectively, at an operating condition of 1.1 kW electric output; no performance degradation of the PEFC system was observed for a month during the DSS test.

In this work, a new method for detecting cathodic second-phase particles on the Mg alloy surface has been developed based on in situ observation of the blade-abraded surfaces of AZ31, AZ61, and 99.9 % pure Mg during the immersion in concentrated alkaline solutions. Continuous local gas evolutions were observed at certain points on the blade-abraded surface, and second-phase particles were found at the same positions, revealing the presence of cathodic particles at the gas evolution sites. The continuous local gas evolution reaction was found to be coupled with not only oxide formation reaction on the Mg matrix around the cathodic particles but also dissolution of Mg at the area within 2–3 μm distance from the cathodic particle. The gas evolution rate appeared to be proportional to the size of cathodic particles, and various cathodic particles containing Fe, Mn, Al, and/or Si were found to be present in the Mg alloys. Based upon the experimental results, it is concluded that the new method is simple, fast, and non-destructive, and it can be used to detect all the cathodic second-phase particles present on the entire surface of Mg alloys, irrespective of the sample shape and size.

In this work, observation of 3-dimensional network structure of open-pores in plasma electrolytic oxidation (PEO) films is reported for the first time using a resin replica method. Conventional plane and cross-sectional views of PEO films provide only 2-dimensional information on the shape and size of pores in PEO films, while an epoxy replica, which was prepared by infiltrating a mixture of liquid epoxy resin and hardener into the open-pores in PEO films under high vacuum and hardening at room temperature, rendered clearly 3-dimensional information about the shape, size and position of open-pores in PEO films. The resin replica method, applied to PEO films on AZ31 Mg alloy formed in phosphate solution, revealed not only 3-dimensional network structures of irregular shape of large size and small size pores, in the middle part and near the film/alloy interface, respectively, but also spherical pores connected to the surface through narrow channels.

Dongjin Metal.Co., Ltd(Received July 9, 2014 ; revised August 4, 2014 ; accepted August 4, 2014)AbstractThe present work is concerned with the formation behavior of anodic oxide films on Al7075 alloy undera galvanostatic condition in 20 vol.% sulfuric acid solution. The formation behaviour of anodic oxide filmswas studied by the analyses of voltage-time curves and observations of colors, morphologies and thicknessesof anodic films with anodization time. Hardness of the anodic oxide films was also measured with anodizationtime and at different positions in the anodic films. Six different stages were observed with anodiziation time: barrier layer formation (stage I), pore formation (stage II), growth of porous films (stage III), abnormalrapid oxide growth (stage IV), growth of non-uniform oxide films (stage V) and breakdown of the thickoxide films under high anodic voltages (stage VI). Hardness of the anodic oxide films appeared to decreasewith increasing anodization time and with the position towards the outer surface. This work provides usefulinformation about the thickness, uniformity, imperfections and hardness distribution of the anodic oxide filmsformed on Al7075 alloy in sulfuric acid solution.

Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was studied in aqueous solutions containing various concentrations of hydroxide ion (OH ? ) and silicate ion (SiO 3 2? ) by voltage-time curves, and corrosion resistance of the PEO film-covered specimen was investigated by immersion test in 0.5 M NaCl solution. From the analyses of the voltage-time curves, it is suggested that two different types of anions are essentially needed for the formation of PEO films on AZ31 Mg alloy: film formation agent and local film breakdown agent. SiO 3 2? ion acts only as a film formation agent but OH - ion acts not only as a film formation agent but also film breakdown agent. The PEO films prepared on AZ31 Mg alloy in alkaline silicate solution showed very good corrosion resistance without any pitting or filiform corrosions up to 480 h of immersion in 0.5 M NaCl.

Corrosion behavior and resistance of plasma electrolyte oxidation (PEO)-treated AZ31 Mg alloy were investigated by immersion and potentiodynamic polarization tests in 0.5 M NaCl solution in view of the PEO film thickness and sealing treatment of the PEO films in boiling water. The PEO films were formed using pulse current for various durations in 1 M NaOH + 0.5 M NaF solution. Filiform corrosion was observed during the immersion test while pitting corrosion occurred during the potentiodynamic polarization test, irrespective of sealing treatment of the PEO films. Corrosion resistance of AZ31 Mg alloy was improved remarkably by the formation of thicker PEO films and their sealing treatments.

The effects of various Zn 2+ concentrations and pH levels (nine conditions in total) on the formation of zinc phosphate conversion coatings (ZPCCs) on AZ31 magnesium alloy were investigated, and corrosion resistances of the coated samples were evaluated by immersion test and potentiodynamic polarization experiment. The corrosion resistance of the coated AZ31 samples was found to increase with increasing Zn 2+ concentration and the lowest corrosion rate was obtained for the samples coated at pH of 3.07, independent of Zn 2+ concentration. The best coatings on AZ31 were obtained at [Zn 2+ ] = 0.068 M and pH 3.07.

Phosphating is one of the most widely used surface treatments of steels and aluminum due to its low-cost, easy mass production, good corrosion resistance and good adhesion with paint. Many researchers have tried to expand applications of the phosphating process, especially to magnesium alloys for automobiles and aerospace applications. Recently, the coatings on magnesium alloys by zinc phosphate conversion coatings (Zn3(PO4)2·4H2O) have been intensively studied. This paper reviews the state-of-the-art of phosphate conversion coatings developed for magnesium alloys, in terms of coating properties, phosphate conversion coatings processes and compositions of phosphating bath.

The effect of the microstructure, particularly of β-Mg 17 Al 12 phase, on the formation and growth of zinc phosphate conversion coatings on magnesium alloy AZ91 (AZ91) was studied. The zinc phosphate coatings were formed on AZ91 with different microstructures produced by heat treatment. The effect of the microstructure on the zinc phosphate coatings were examined using optical microscope (OM), X-ray diffraction (XRD), coatings weight and etching weight balances, scanning electron microscopy (SEM) and salt immersion test. Results showed that as-cast AZ91 contained a high volume fraction of the β-Mg 17 Al 12 phase and it was dissolved into α-Mg phase during heat treatment at 400 °C. The β-phase became center for hydrogen evolution during phosphating reaction (cathodic sites). The decreased volume fraction of the β-phase caused decreasing both coatings weight and etching weight of the phosphating process. However, it increased the crystal size of the coatings and improved corrosion resistance of AZ91 by immersing in 0.5 M NaCl solution. Results also showed that the structure of the zinc phosphate conversion on AZ91 consisted of two layers: an outer crystal Zn 3 (PO 4 ) 2 ·4H 2 O (hopeite) and an inner which was mainly composed of MgZn 2 (PO 4 ) 2 and Mg 3 (PO 4 ) 2 . A mechanism for the formation of two layers of the coatings was also proposed in this study.

A.c. impedances of mechanically polished CP-Ti specimens were measured at open-circuit potential (OCP) with immersion time and under applied anodic potentials between −0.2 and 1 VAg/AgCl in 0.1 M NaOH solution. Capacitances of native oxide films (Cox,na) grown naturally and capacitances of anodic oxide films (Cox,an) formed under applied anodic potentials were obtained to examine the growth of native and anodic oxide films in 0.1 M NaOH solution and how to use Cox,na for the surface area measurement of Ti specimen. 1/Cox,na and 1/Cox,an appeared to be linearly proportional to OCP and applied potential (Eapp), with proportional constants of 0.086 and 0.051 uF �1 V �1 , respectively. The Cox,na also appeared to be linearly proportional to geometric surface area of the mechanically polished CP-Ti fixture specimen, with proportional constants of 11.3 and 8.5 µF cm �2 at −0.45 VAg/AgCl and −0.25 VAg/AgCl of OCPs, respectively, in 0.1 M NaOH solution. This linear relationship between Cox,na and surface area is suggested to be applicable for the measurement of real surface area of Ti specimen.

Anodic oxidation behaviour of Mg–Sn alloys was studied to elucidate the effect of Sn content in Mg alloy on the formation of anodic films in alkaline solutions. The anodic films become less resistive by the presence of Sn in Mg in 0.1 M NaOH, while the anodic films formed in 0.1 M NaOH + 0.1 M KF becomes more resistive with increasing Sn content in Mg. Generation of microarcs during the anodizing was observed only in a fluoride-containing solution for Mg–6Sn and Mg–8Sn. Corrosion resistance of the anodized Mg–Sn alloys in the fluoride-containing solution increased with increasing Sn content in Mg.

TiO2 nanotubes were formed on Ti electrochemically by the application of anodic current in 1 M H3PO4 + 0.3 M HF solution in a glass and Teflon bath. The TiO2 nanotubes could be partly grown in the glass bath while a uniform growth of TiO2 nanotubes was observed over the whole surface in the Teflon bath. The TiO2 nanotubes fabricated in the glass bath broke off readily during ultrasonic cleaning in distilled water while the TiO2 nanotubes formed in the Teflon bath was not damaged by the ultrasonic cleaning up to 5 minutes. The ultrasonic cleaning could remove the surface residuals which are obtained inevitably if TiO2 nanotubes are fabricated in aqueous solutions.

nanotubes were formed on Ti by anodizing in 1 M + 0.3 M HF and 0.1 M + 2% in ethylene glycol, and their surface and cross-sectional morphologies were observed using FE-SEM as a function of anodizing time and applied voltage. The cross-section of the nanotubes was readily observed from the small pieces of nanotubes remaining near the scratch lines after scratching of the anodized surface. nanotubes was observed to grow faster and thicker in non-aqueous solution than in aqueous solution. Diameter of nanotubes was proportional to the applied voltage, irrespective of the type of the electrolyte, and it is recommended to use non-aqueous solutions for the preparation of larger diameter of nanotubes.

This work is concerned with the effects of Ca-ion implantation on the electrochemical behavior and biocompatibility of commercially pure Ti. The electrochemical behavior was tested by open-circuit potential transient and polarization experiments in Hanks' solution, and the biocompatibility was evaluated by soaking in simulated body fluid solution. The Ca-implanted Ti specimen showed more active electrochemical behavior than non-implanted specimen, and easier formation of apatite with good Ca / P ratio in the range of 1.38 and 1.60, revealing its potential as a bioactive material.