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Friction stir processing (FSP) was used to improve the mechanical characteristics and microstructure of AC7AV cast Al–Mg alloy. The mechanical characteristics of AC7AV deteriorated due to significant defects caused by excessive friction heat after being subjected to multi-pass FSP. An alternative method of multi-pass FSP with two traveling directions was used to solve the defect problems in multi-pass FSP for cast AC7AV Al alloy. The results of various multi-pass FSP experiments showed that the mechanical properties of the cast AC7AV Al alloy specimens subjected to this alternative multi-pass FSP were better than those produced by the conventional multi-pass FSP method.

We investigated the optimal method of application and the anticorrosive abilities of Zn , Al , and Zn + 15%Al spray coatings in protecting stainless steel 304 (STS304) in sea water. If a defect such as porosity or an oxide layer, causes STS304 to be exposed to sea water, and the thermal spray coating material will act as the cathode and anode, respectively. The Tafel experiments revealed that Al -coated specimens among applied coating methods had the lowest corrosion current densities. As the corrosion potential decreases with increasing corrosion current density, we estimated the characteristics and lifetime of the protective thermal spray coating layer in the galvanic cell formed by the thermal spray coating layer and STS304.

The effect of heat treatment on the electrochemical and mechanical properties of SS400 steel was investigated, and the effects of annealing conditions on notched specimens subjected to the slow strain rate test (SSRT) were studied. The results show that no correlations are observed among the maximum tensile strength, yield strength, and stress corrosion cracking. In contrast, the elongation and time-to-fracture are improved with stress-relieving annealing compared with the as-received condition. The elongation, time-to-fracture, and number of dimples increase with annealing heat treatment.

The electro-clean system (ECS), a ballast water management system that eliminates harmful aquatic organisms in ship ballast water via electrochemically produced chloride, was developed. The current density for potentiostatic experiments subjected to seawater with an applied potential (−0.1 V) at various TRC concentrations (2×10−6, 6×10−6, 10×10−6, and 15×10−6) have similar results. The current density at −0.1 V has the highest value compared with that at −0.7 V and −0.4 V. For all concentrations, the current density increases with increasing applied potential.

The synthesis of a new series of 1beta-methylcarbapenems having cyclic sulfonamide moieties is described. Their in-vitro antibacterial activities against both Gram-positive and Gram-negative bacteria were tested and the effect of a substituent on the pyrrolidine ring was investigated. One particular compound IIIe having a [1,2,5]thiadiazolidin 1,1-dioxide moiety showed the most potent antibacterial activity.

The mechanical characteristies for friction stir welding (FSW) of 5083-O Al alloy were evaluated. The results show that in FSW at 800 r/min and 124 mm/min, a weld defect is observed at the start point. However, the button shape at the end point is good and the stir zone has a soft appearance. At 267 mm/min, a void occurs at the button. A slight weld defect and rough stir zone are seen both at the start and end points at 342 mm/min. Moreover, at the bottom, a tunnel-type void is observed from an early stage to the end point, and at 1 800 r/min, a weld defect can be found from an early stage to the end point. These defects are rough with imperfect joining due to excessive rotation speed and high physical force. Weld fractures relative to rotational and travel speeds are observed at the stir zone. The optimum FSW conditions are a welding speed of 124 mm/min and a rotational speed of 800 r/min.

The corrosion protection property and morphology of colloidal silica conversion films as an alternative to chemical conversion coating(CCC) films were examined. The corrosion behavior was investigated in 3%NaCl solution using electrochemical techniques. Corrosion was implied by the appearance of red rust on the specimen surface. The results show that in 3%NaCl solution, red rust appears at 15–20, 55–70, and 75–85 d on Zn-electroplated steel, colloidal silica conversion-coated specimens, and chemical conversion-coated, specimens, respectively. In the salt spray test, the colloidal silica film provides better corrosion protection than CCC film, i.e., red rust appears at 96 h on the Zn-electroplated steel sheet, at 432 h on the CCC films, and at 888 h on silica conversion coating.

Electrochemical tests were undertaken to determine the optimum conditions in seawater for corrosion protection of friction stir-welded 5083-O Al alloy. Polarization trend observations show that the limiting potential that avoids the effects of hydrogen embrittlement is −1.6 V, corresponding to the crossover point between concentration polarization and activation polarization. However, the optimum protection potential is between −1.5 and −0.7 V since the current density at these values is low in the potentiostatic tests. When a galvanic cell is formed in the seawater, the welds exhibit electrochemically stable trends. Welded parts in galvanic tests with various area ratios are stable and have excellent anticorrosion characteristics.

Thermal spray coating presents a sacrificial-anode cathodic protection method since differences between the potentials of materials are employed. If a base metal is exposed to seawater, due to defect in the thermal spray coating, the metal is protected by the sacrificial anodic characteristics of the coating layer because micro-cells formed by the base metal and the thermal spray coating act as cathodes and anodes, respectively. The coating thickness has little effect on the surface morphology of the coating. However, the electrochemical properties with the increasing of coating thickness present good results.

The chemical conversion coating was formed on Mg alloy for low cost and harmlessness in environment by using the colloidal silica as the main component. The film formed at 298 K was thick, which was thought to be the combination of Si and O. In salt spray test, the ratio of black rust on the specimen that did not conducted chemical conversion treatment was five times or more than those of the chemical conversion treated specimen. The film of chemical conversion coating produced by alkali treatment process was thinner than the specimen produced in basic chemical conversion treatment solution.

Aluminum alloys are used as substitutes for fiber reinforced polymer(FRP) in ships and boats. However, ships constructed with 5000-series Al alloy suffer a little corrosion in the marine environment, when they run in high speed, and high flow rate, etc. Therefore, solution heat treatment was carried out to prevent corrosion. The optimal heat treatment involved heating specimens for 120 min at 420 °C and then cooling them in water. In addition, the optimal ageing condition involved ageing specimens for 240 min at 180 °C. The slow strain rate test(SSRT) in a seawater revealed that heat treatment under optimal conditions produced improved elongation, time-to-fracture and amount of dimples compared with the as-received specimen.

Stainless steels such as STS 304, 316 and 630 are frequently used as shaft materials in small fiber reinforced polymer (FRP) fishing boats. If the shaft material is exposed to a severely corrosive environment such as seawater, it should be protected using appropriate methods. The impressed current cathodic protection was used to inhibit corrosion in shaft materials. In anodic polarization, passivity was remarkably more evident in STS 316 stainless steel than in STS 304 and STS 630. The pitting potentials of STS 304, 316, and 630 stainless steels were 0.30, 0.323, and 0.260 V, respectively. The concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation were evident in the cathodic polarization trends of all three stainless steeds. STS 316 had the lowest current densities in all potential ranges, and STS 630 had the highest. Tafel analysis showed that STS 316 was the most noble in the three. In addition, the corrosion current density was the lowest for STS 316.

The construction of fiber-reinforced plastic (FRP) boats is decreasing trend since the application of international regulations on the control of marine environmental pollution, which recommended the use of environmentally friendly materials. The aluminum alloy used with material for ship is a superior to FRP. It is environmental friendly, easy to recycle, and provides a high added value to fishing boats. However, the welding for Al alloy materials have many problems, such as deformation by welding heat and effect of the working environment. In this paper, it was carried out welding by robot with welding material of ER5183 and ER5556 on 6061-T6 Al alloy for ship. The mechanical and electrochemical characteristics evaluated for specimen welded by robot. The cathodic polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. The hardnesses of welding zone and heat affected zone are lower than that of base metal. At the result of tensile test, the specimen welded with ER5183 presented excellent property compared with ER5556.

In the study, it was carried out dissimilar metal welding on materials for Al ship. The electrochemical and mechanical characteristics evaluated for specimen welded by ROBOT. The hardness of welding zone is lower than those of heat affected zone and base metal. At the result of tensile test, the specimen welded with ER5183 welding material presented excellent property compared with ER5556. The polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. At the Tafel experiments result, the corrosion density in welded with ER5183 welding material presented the lowest value.

Friction stir welding(FSW) was developed as a new solid state welding technique by The Welding Institute (TWI). On the basis of FSW, a new processing technique, friction stir processing (FSP), has recently been developed. FSP has been applied to cast aluminum alloy to modify the microstructure to enhance mechanical characteristic. FSP is a new solid state processing technique for microstructural modification in metallic materials. FSP has been applied to aluminum alloy to modify the microstructure to enhance mechanical characteristic. In this study, we investigated optimum condition friction stir processing with the evaluation of mechanical characteristic for 5456-H116 Al alloy. The mechanical characteristics of base metal similar with in 15 mm/min, 250 RPM with full screw probe. This condition is concluded that optimum friction stir processing condition. The result of this investigation will be able to application for repair of welding part for aluminum ship.

This study examined the effects of multiple mechanical forces on gas exchange and hemolysis in intravascular lung assist devices (IVLAD). Specific attention was paid to on the effect of membrane vibration. This study adhered to the recommended practice for the assessment of hemolysis described by the American Society of Testing and Materials (ASTM). The results showed a higher oxygen (O 2 ) transfer rate and carbon dioxide (CO 2 ) removal rate in each excited frequency bandwidth than those without vibration. The maximum oxygen transfer and carbon dioxide removal rate occurred at frequency band of 7 Hz. The gas exchange improved maximum 52%. The plasma-free hemoglobin was 11.2 ± 0.57 and 14.4 ± 0.74 mg/100 ml by exciting a piezo-vibrator with a sinusoidal wave magnitude of DC10 V and DC50 V, respectively. The NIHO value was determined to be 59 ± 2.76 and 95 ± 4.32 mg/100 ml by exciting a piezo-vibrator with a sinusoidal wave magnitude of DC10 V and DC50 V, respectively. In conclusion, piezoelectric lead zirconate titanate (PZT) materials are exciting systems for improving the oxygen transfer efficiency and blood suitability of hollow fiber membrane in the development of new IVLAD.

The purpose of this study was to investigate the effect of multiple mechanical forces in gas exchange and hemolysis in an intravascular lung assist device (IVLAD). Specific focus was given to the effect of membrane vibration. We designed the oscillatory type artificial lung assist device attached with a polyvinylidene fluoride sensor and a lead zirconate titanate (PZT) actuator (vibrator). Maximum oxygen transfer occurred at a frequency of 7 Hz for bovine blood and 35 Hz for distilled water. The normalized index of hemolysis oxygenator values for the circuit was 0.0014 g/mL for excitation of the PZT actuator with a sinusoidal 10-V wave and 0.0018 g/mL for a 50-V wave. The experiment results indicate effective performance in enhancing the gas transfer of the IVLAD. This novel hollow membrane filter IVLAD design demonstrates an acceptable level of gas exchange performance with an acceptable level of blood compatibility, and so it has potential as an implantable lung assist device for patients with acute respiratory distress syndrome.

We investigated the mechanical and electrochemical properties of aluminum alloys. Aluminum alloys do not corrode due to the formation of an anti-corrosive passive film, such as Al2O3 or Al2O3·3H2O, which resists corrosion in neutral solutions. In seawater, however, Cl − ions destroy this passive film. The current density in the first passivity range during the application of anodic protection had a similar value as that for concentration polarization by dissolved oxygen during the application of cathodic protection. The current density in the first passivity range had the lowest value overall. The lowest current densities in the potentiostatic and galvanostatic tests occurred at potentials of −1.4 to −0.7 V and −0.9 to −0.7 V, respectively.

In friction stir welding for 6061-T6 with various traveling speed and rotation speed conditions, the best mechanical characteristics presented in traveling speed of 507 mm/min and rotation speed of 1100RPM. The maximum tensile strength and yield strength increased with the increasing of traveling speed. The result of the electrochemical characteristic evaluation in friction stir welding at optimum conditions for 6061-T6 Al alloy presented a good characteristics compare to base metal.

Small FRP(fiber-reinforced polymer) fishing ships have numerous problems with the point of the environmental and recycling perspectives. In light of these aspects, aluminum can be used as a material for ship building. It is environmental friendly, easy to recycle, and provides a high added value to fishing boats. In this paper, we report on mechanical and electrochemical characteristics of welding parts for friction stir welded 5456-H116 Al alloy. In friction stir welded at various traveling speeds under the rotation speed of 500 RPM, the best characteristics presented in traveling speed of 15mm/min. The anodic polarizations of base metal and welding metal were observed tendency which current density from the open circuit potential suddenly increase. The cathodic polarization presented concentrated polarization caused by the dissolved oxygen reduction reaction and activation polarization caused by hydrogen generation. From result of Tafel analysis, the corrosion potential of 5456 alloy(Base metal) was lower than that of friction stir welded part, as were its corrosion current densities.

Atomic force microscopy (AFM) has become an attractive technique to fabricate nano devices since the observing mechanism is different from fabricating one. We have fabricated the superconducting flux flow transistor (SFFT) with a serial-channel structure using the AFM lithography analyzed the modified surface by the AFM image. We investigated the induced voltage in a serial-channel terminals dependence on the gate current by the I–V measurement system. We performed the numerical simulation to get the theoretical characteristics of the SFFT controlled by the gate current via the modified channel. The transresistance was 0.006 Ω for Id=51 mA at Ig=5 mA. It is very low transresistance in comparison with SFFTs fabricated by the other processes, however our results show that the SFFT with a serial-channel structure is effectively fabricated by an AFM lithography method.

We report on the optimum corrosion protection potential range for stress corrosion cracking and hydrogen embrittlement of 5083-H112 Al alloy specimens using electrochemical methods and slow strain rate testing (SSRT) in seawater. In the results of the cathodic polarization curve, the concentration polarization due to dissolved oxygen reduction reaction correspondeds to a protection potential of OCP≈ −1.55 V. However, a potential of −1.2 V in the SSRT showed little effect of atomic hydrogen evolution. Potentials less than −1.6 V are affected by atomic and molecular hydrogen. We thus concluded that the effect of atomic hydrogen predominates. Overall, the optimum corrosion protection range for SCC and hydrogen embrittlement of 5083-H112 seems to be between −0.9 V and −0.7 V.

Recently, there has been a new appreciation of aluminum alloys as materials that are capable of reducing the environment load. This is because aluminum alloys are lightweight, easy to recycle, permit miniaturization, and have environmental friendly properties. In this study, we investigated the mechanical and electrochemical properties of 5083F aluminum alloys using slow strain rate test(SSRT) and potentiostatic tests under various potential conditions. In the potentiostatic tests, the current density in the potential range from -0.7 to -1.4V after 1,200 s was low. After considering the results of the potentiostatic tests, maximum tensile strength, yield strength, elongation, time-to-fracture, observation of fractured specimen and fractography analysis, the optimum protection potential range was between -1.3 and -0.7V(Ag/AgCl).

The demand for high performance, integrity, and miniaturization in the area of electronic and mechanic devices has drawn interest in the fabrication of nanostructures. However, it is difficult to fabricate the channel with nano-scale using a conventional photography techniques. AFM anodization technique is a maskless process and effective method to overcome the difficulty in fabricating a nano-scale channel. In this paper, we first present a new fabrication of a single-channel SFFT using a selective oxidation process induced by an AFM probe. The modified channel was investigated by electron probe microanalyzer (EPMA) to find the compositional variation of the transformed region. In order to confirm the operation of a single-channel SFFT, we measured the voltage–current characteristics at the temperature of liquid nitrogen by an I – V automatic measurement system. Our results indicate that the single-channel SFFT having effect as a weak link is effectively fabricated by an AFM lithography process.

The synthesis of a new series of 1β-methylcarbapenems having cyclic sulfonamide moieties is described. Their in vitro antibacterial activities against both Gram-positive and Gram-negative bacteria were tested and the effect of substituent on the pyrrolidine ring was investigated. A particular compound (IIIi) having 2-methyl-[1,2,6]thiadiazinan-1,1-dioxide moiety showed the most potent antibacterial activity.

We studied the effects of solution RPM, bath temperature, and time in anodizing AZ91 under a constant current density of 750 mA/cm2 in a 1 M NaOH solution. In general, increasing the anodizing time, RPM, and temperature of the bath improved the corrosion resistance. The thickness of the anodic oxide film likely grew by increasing the time required to generate the active dissolution reaction. When anodizing at 750 mA/cm2, we evaluated a 300–3600-s range in anodizing time, 0–1500 RPM, and 296–373 K bath temperatures, and determined that 3600 s, 1500 RPM, and 373 K comprised the optimum conditions.

As a reactor coolant pump(RCP) is operated in the nuclear power system for a long time. so its surface is continuously contaminated by radioactive scales. In order to perform regular or emergency repair about RCP internals a special decontamination process should be used to reduce the radiation from the RCP surface by means of chemical cleaning. In this study, applicable possibility in chemical decontamination for RCP was investigated on the various materials. The STS 304 showed the best electrochemical properties for corrosion resistance than other materials. However, the pitting corrosion was slightly generated in both STS 415 and STS 431 with the increasing numbers of cycle and intergranular corrosion were sporadically observed. The size of their pitting corrosion and intergranular corrosion were also increased with increasing cycle numbers.

Al alloy is a highly active metal but forms a protective oxide film having high corrosion resistance in atmosphere environment. However, the oxide film is not suitable for practical use, since the thickness of the film is not uniform and it is severly altered with formation conditions. This study focused on developing an aluminum anodizing layer having hardness, corrosion resistance and abrasion resistance equivalent to a commercial grade protective layer. Aluminum anodizing layer was produced by two-step aluminum anodizing oxide (AAO) process with different sulfuric acid concentrations, and the cavitation characteristics of the anodized coating layer was investigated. In hardness measurement, the anodized coating layer produced with 15 vol.% of sulfuric acid condition had the highest value of hardness but exhibited poor cavitation resistance due to being more brittle than those with other conditions. The 10 vol.% of sulfuric acid condition was thus considered to be the optimum condition as it had the lowest weight loss and damage depth.

Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiber-reinforced plastic (FRP). Aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. We investigated the mechanical and electrochemical properties of aluminum alloys using slow strain rate and potentiostatic tests under various potential conditions. Aluminum and aluminum alloys do not corrode due to the formation of an anti-corrosive passive film, such as Al2O3 or Al2O3·3H2O, which resists corrosion in neutral solutions. In seawater, however, Cl− ions destroy this passive film. The optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between −1.5 and −0.7 V (SSCE). These results can be used as reference data for ship design.

A series of electrochemical experiments on Al alloys were undertaken to determine their optimum protection potentials in seawater. With 1050 and 5456 alloys, passive films form during anodic polarization but are destroyed by the Cl in seawater, only to regrow as a result of the self-healing capacity of aluminum. The current density of 5456 Al alloy proved to be lower than that of 1050 as a whole. Any shift to more anodic or cathodic conditions in the potential range of-1.5∼-0.68 V resulted in a sudden increase in current density. Current densities in the high-strength 7075 Al alloy showed the greatest values. In contrast, the current densities of 5456 alloy, known to have excellent corrosion resistance in seawater, were the lowest in the range of -0.70∼-1.3 V, and we concluded that this potential range offered optimal protection.

Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiber-reinforced plastic (FRP). This is because aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. In this study, we investigated the mechanical and electrochemical properties of aluminum alloys using the slow strain rate and potentiostatic tests under various potential conditions. The optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between -1.5 and -0.7 V (SSCE). These results can be used as reference data for ship design.

This paper investigated the effects of anodizing time on the formation of anodic oxide films on a Mg-Al alloy in alkaline solution. The thickness of the anodic oxide film was increased by increasing the time required to generate the active dissolution reaction. When anodizing at various anodizing time, the potential after passivity increased with time, which implies growth in film thickness. When the anodizing time was varied, the quantity of oxygen increased with time in the white areas (the film), i.e., more film was observed in the SEM and EDX analyses.

Magnesium must be surface treated to prevent corrosion, since it is a very active metal electrochemically. On anodizing, a compact film several tens of micrometers thick forms on magnesium, which imparts good corrosion resistance. The Mg-Al alloy (AZ91) was anodized in 1 M NaOH solution. The surface morphology of the anodized films was observed using scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), and electrochemical methods. The effects of current density on the formation of anodic oxide films for a Mg-Al alloy in 1 M NaOH were investigated. In the anodic polarization curve, the reference corrosion potentials were far greater at 4-9 mA/cm2 than at 1 mA/cm2. The film that formed at 1 mA/cm2 was thin, suggesting that parts of the film had been dissolved or destroyed during the anodic polarization test. Corrosion resistance differed owing to concentric differences in current flow. Thick anodic oxide films were formed at higher applied currents.

FRP (fiber-reinforced polymer) ships used with small boats for fishing pose numerous problems related to both the environment and recycling. From this perspective, aluminum offers an environmentally friendly substitute for FRP that is easy to recycle and imparts a high added value to fishing boats, with a reduction in fuel demands. The current density of 7075 Al alloy increases linearly with an increase in potential during anodic polarization, which implies that no passivation of this alloy occurs. With 1050 and 5456 alloys, passive films form during anodic polarization but are destroyed by the Cl in seawater, only to regrow as a result of the self-healing capacity of aluminum. A shift to more anodic or cathodic conditions in the potential range of –1.5 ~ –0.68 V resulted in a sudden increase in current density. Current densities in the high-strength 7075 Al alloy showed the greatest values. In contrast, the current densities of 5456 alloy, known to have excellent corrosion resistance in seawater, were the lowest in the range of –0.70 ~ –1.3 V, and we conclude that this potential range offers optimal protection.

The purpose of this study was to assess and quantify the beneficial effects of gas exchange according to the various frequencies of the sinusoidal wave that are excited by a PZT actuator, on patients suffering from acute respiratory distress syndrome (ARDS). In this study, an experimental method for the flow hydrodynamics was developed through a bundle of sinusoidally vibrated hollow fibers to observe how well vibrations might enhance the performance of the VIVLAD. We measured the effect of the various excitation frequencies of the PZT actuator on the gas transfer rates and hemolysis from the maximum gas transfer rate. As a result, the maximum oxygen transfer rate was reached at the maximum amplitude and through the transfer of vibrations to the hollow fiber membranes. The device was maximum excited by a frequency band of 7 Hz at various water flow rates, as this frequency was the 2nd mode resonance frequency of the flexible beam. 675 hollow fiber membranes were also bundled, within the blood flow, into the device.

The electrochemical and mechanical properties of welded high-strength steel were investigated using the slow strain rate test method with a constant applied cathodic potential. No correlations were found with the maximum tensile strength, yield strength, stress at failure, or hydrogen embrittlement. However, the elongation, time-to-fracture, and strain-to-failure ratio decreased as the potential became more negative. These parameters were greatest when the potential was -770mV, regardless of the post-weld heat treatment conditions. The elongation and time-to-fracture increased with PWHT.

The effects of sealing solutions on the corrosion resistance of anodized Mg-Al alloys were investigated. As the proportion of Mg(OH)2 increases with the increase in the NaOH concentration, the corrosion potential improves. The sealing effects were further improved by increasing the temperature of distilled water, the pH of solutions, and the proportion of Mg(OH)2 present in the anodic film.

Electrochemical properties and mechanical properties of welded high strength steel were investigated by the slow strain rate test (SSRT) method with an applied constant cathodic potential. There was no correlation between maximum tensile strength, yield strength, stress at failure, and hydrogen embrittlement. However, the elongation, time-to-fracture, and strain-to-failure ratio decreased with shifting potential of the negative direction. Elongation, time-to-fracture, and strain-to-failure ratio for the various welding methods displayed the highest values when the potential was −770 mV regardless of post-weld heat treatment (PWHT) conditions. The elongation, time-to-fracture, and amount of dimples by PWHT were increased. The optimum potential region for cathodic protection without hydrogen embrittlement was observed between −770 and (above) −850 mV (SCE) in the post-weld specimens heat treated at 550°C and the as-welded specimens.

Mg alloys were anodized in alkaline NaOH solutions with various additives as a non-chromate method. Specimen AZ91 was anodized at a potential that produced a strong surface dissolution reaction and generated a large amount of Mg(OH)2. The effect of sealing after anodizing was investigated, focusing on the effects of sealing time, temperature and solution conditions. The current density decreased with increasing A1(OH)3 concentration in 1 M NaOH solution during anodizing; sparking occurred at potentials above 80 V. The best corrosion resistance with anodizing in 1 M NaOH solution occurred at a potential of 4 V, which caused the strongest active dissolution reaction. The sealing effect improved with increasing time and temperature, and corrosion resistance was proportional to the relative ratio of Mg(OH)2. If the oxygen thickness observed by EDX equaled the film thickness, the film formed at 4 V in 1 M NaOH was 10–15 Μm thickness. The optimum corrosion resistance in sealing at various solutions after anodizing was 1M-NaOH solution.

The state in which a stainless steel (STS) exhibits a very low corrosion rate is known as passivity, which is self-healing in a wide variety of environments. However, for those STS the corrosion includes pitting, crevice corrosion, galvanic corrosion, hydrogen embrittlement and stress corrosion cracking etc. And the corrosion resistance of STS is affected by area ratio, solution temperature and solution condition etc. Corrosion characteristics of STS 304, welding parts STS 316, STS 329 and STS 444 were investigated with parameters such as corrosion potential, galvanic current measurements, cathodic and anodic polarization behaviors as a function of area ratio and solution temperature in solution for hot water tank. It was found that galvanic current is affected by the area ratio, temperature and a kind of STS for hot water tank. Corrosion potential of welding part STS 316 was lower than that of STS 304, STS 329, STS 444 in solution for #1, #2 hot water tank. Therefore, it is suggested that the welding part STS 316 acts as anode for the other STSs. The amplitude of galvanic current between welding parts STS 316 and STS 304, STS 329, STS 444 in #1 solution is smaller than that in #2 solution. This is the reason that chloride ion quantity in #2 solution is more than that for #1 solution. And then welding part STS 316 corrodes easily by acting as anode compared to the other STS.

The electrochemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH) 2 in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH) 2 was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in a phase, which had a lower Al content. In the anodic polarization test in 0.017 mol.dm - 3 NaCl and 0.1 mol.dm - 3 Na 2 SO 4 at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the a phase is a non-compacted film. The anodic film on the a phase at 30 min was a compact film as compared with that at 10 min.

Evaluation of corrosion resistance of material surface was investigated with electrochemical factors, such as corrosion potential, corrosion current density with parameters of as-welded, post-weld heat treatment (PWHT) of 550, 600, 650 °C for a RE36 steel and mechanical properties such as elongation, hydrogen embrittlement and analysis of SEM fractography were also investigated with slow strain rate test (SSRT) method with applied constant cathodic potential in case of as-welded and PWHT of 550 °C. An optimum temperature for corrosion resistance improvement was apparently observed at 550 °C of PWHT and elongation was also increased with PWHT of 550 °C than that of as-welded condition. Therefore, the susceptibility of hydrogen embrittlement was considered to be decreased with PWHT of 550 °C compared to that of as-welded condition and to be increased according to potential shifting in the low direction.

Marine structures exposed to severe marine environment should be protected against corrosion in an appropriate way. The cathodic protection method is being widely used in marine structural steel, however, high strength steel for marine structures is easily affected by hydrogen embrittlement (HE) at heat affected zone parts due to over-treatment during impressed current cathodic protection. Elongation and time to fracture were decreased due to HE with shifting to low potential, however, the susceptibility of HE was decreased by post-weld heat treatment (PWHT). It is suggested that an optimum cathodic protection potential not causing HE is from −770 mV (SCE) to above −875 mV (SCE) regardless of PWHT condition.

Impressed current cathodic protection can result in hydrogen embrittlement, which can cause trouble with high-strength steels, particularly at welds. Therefore, the limiting potential for hydrogen embrittlement should be examined in detail as a function of the cathodic protection potential. This study investigated the effects of post-weld heat treatment (PWHT) on marine structural steels from an electrochemical viewpoint. In addition, the slow strain rate test (SSRT) was used to investigate both the electrochemical and mechanical effects of PWHT on impressed current cathodic protection. According to the SSRT, the optimum cathodic protection potential was −770 mV [with a saturated calomel electrode (SCE)]. SEM fractography analysis showed that the fracture morphology at an applied cathodic protection potential of −770–850 mV (SCE) was a dimpled pattern with ductile fractures, while a transgranular pattern was seen at potentials below −875 mV (SCE). Therefore, the cathodic protection potential range should be −770–850 mV (SCE).

Chemical conversion treatment of Mg−Al alloy (AZ91) using colloidal silica as an alternative to chromate conversion was investigated as a function of solution pH, temperature, solution conditions, and treatment time. The solution used for the colloidal silica coating consisted of colloidal silica, titanium sulfate, and cobalt ions to maintain good anti-corrosion and adhesion properties. Adding CoSO4 to the colloidal silica solution enhanced the adhesion force between the silica film and magnesium substrate. The optimum conditions for the chemical conversion treatment solution were pH 2, 90-sec treatment, and 25°C.

Colloidal silica films were produced on zinc-electroplated steel using a new chemical conversion treatment, which provides an alternative to chromate conversion coating. The treatment solution consisted of colloidal silica, titanium sulfate, cobalt sulfate and nitrate ions at 298K, pH2. The corrosion resistance of the film coated specimens was estimated by impedance measurement in a sodium chloride solution for 8 days.The effects of colloidal silica concentration, treatment time and additive ions on corrosion resistance and adhesion of the film were investigated. The addition of titanium sulfate to the colloidal silica solution changed the surface potential of silica particles from negative to positive and improved the film characteristics. The addition of cobalt sulfate enhanced the adhesion between the zinc on the steel and the silica film. The film was not formed without nitride ions. Chemical conversion for 90s in a solution containing 200mM colloidal silica, 4.2mM titanium sulfate, 1.8mM cobalt sulfate, 4.2mM succinic acid and ajusted pH2 by nitric acid at 298K showed excellent film characteristics.

The chemical conversion of zinc-electroplated steel sheet using colloidal silica was investigated as an alternative to chromate conversion. The corrosion resistance of zinc-electroplated steel sheet with and without this treatment was estimated from electrochemical impedance spectroscopy, open circuit potential in 3 mass% NaCl solution and the salt spray test. The solution used for the colloidal silica coating consisted of colloidal silica, titanium sulfate, cobalt sulfate, and succinic acid. This solution produced an adhesive film and maintained good corrosion resistance. Adding cobalt ions to the colloidal silica solution enhanced the adhesion between the silica film and the zinc layer electroplated on the steel sheet. In the electrochemical impedance analysis, the corrosion protection conferred by the colloidal silica film was about five times greater than that of a normal zinc-electroplated steel sheet, but not as good as that of a chromate film. In the salt spray test, rust appeared more quickly on chromate-coated specimens than on colloidal silica film surfaces.

The formation behavior and corrosion characteristics of anodic oxide films on pure magnesium and on Mg-Al alloys were investigated, focusing on the effects of anodization potential, aluminum content, temperature, and NaOH concentration. Pure magnesium and Mg-Al alloys were anodized for 600s at 3, 10, 40, and 80V in NaOH solutions. It was found that the anodic film formed at 3 V had the best corrosion resistance, regardless of temperature, NaOH concentration, or aluminum content. An especially high current density was observed at applied potentials of 3-7 V on anodization in alkaline NaOH solutions. XRD analysis detected Mg(OH) 2 and MgO peaks in the films on the anodized specimens. The relative intensity of the Mg(OH) 2 XRD peaks decreased with increasing applied potential, while those of MgO increased. Mg(OH) 2 was generated by an active dissolution reaction with high current density at the specimen surface. Generation of Mg(OH) 2 increased with increasing temperature, while that of MgO increased with NaOH concentration. Moreover, the current density after anodization for 600 s at a constant potential decreased with increasing aluminum content in Mg-Al alloys.

The cathodic protection method is being widely used in marine structural steel. However, a high tensile steel such as RE 36 steel used for marine structural steel is easily susceptible to hydrogen embrittlement due to overprotection as well as the preferential corrosion of the heat affected zone (HAZ). In this paper, corrosion resistance and mechanical properties were investigated from the electrochemical view and mechanical view in as-wedded and post-weld heat treated specimens. Fracture surface was analyzed by SEM. The corrosion resistance in post-weld heat treated at 550°C was superior to that at other post-weld heat treatment (PWHT) temperature. On the other hand, elongation was decreased with a shift to the low potential direction which may cause hydrogen embrittlement. And a quasi-cleavage (Q.C) fracture mode was also observed significantly with a potential increase to the active direction.