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Zenji Horita - One of the best experts on this subject based on the ideXlab platform.
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Effects of High-Pressure Torsion on the Pitting Corrosion Resistance of AluminumIron Alloys
Materials Transactions, 2013Co-Authors: Hiroaki Nakano, In Joon Son, Satoshi Oue, Zenji Horita, Hiroto Yamaguchi, Yohei Yamada, Hiroki KogaAbstract:The effects of reducing the grain size by high-pressure torsion (HPT) on the Pitting Corrosion resistance of AlFe alloys with Fe contents of 0.5, 2 and 5mass% were investigated by means of polarization curves in solutions containing 0.1mol·dm ¹3 Na2SO4 and 8.46mmol·dm ¹3 NaCl (300ppm Cl ¹ ) at 298K and by surface analysis. The potentials for Pitting Corrosion of the AlFe alloys were clearly shifted to the noble direction by HPT, leading to an improvement in Pitting Corrosion resistance. This improvement was larger in the Al0.5%Fe and Al2%Fe alloys and smaller in the Al5%Fe alloy. The AlFe alloys contained precipitates of AlFe intermetallic compounds, around which Pitting Corrosion occurred. The Al5%Fe alloy, in particular, contained large precipitates tens of micrometers in size, and Pitting Corrosion was significant around these large precipitates. It is evident from the time-dependence of the Corrosion potential and the polarization resistance of the Corrosion reaction that the formation rate of Al oxide films increases as a result of HPT. It was therefore concluded that the improvement in Pitting Corrosion resistance of the AlFe alloys with HPT is caused by increasing the oxidation rate of Al. [doi:10.2320/matertrans.MH201301]
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Effect of Equal-Channel Angular Pressing on Pitting Corrosion of Pure Aluminum
International Journal of Corrosion, 2012Co-Authors: In Joon Son, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fukushima, Zenji HoritaAbstract:The effect of equal-channel angular pressing (ECAP) on the Pitting Corrosion of pure Al was investigated using electrochemical techniques in solutions containing 0.1 m mol·dm−3 of Na2SO4 and 8.46 mol·dm−3 of NaCl (300 ppm Cl−) and followed by surface analysis. The potential for Pitting Corrosion of pure Al was clearly shifted in the noble direction by the ECAP process indicating that this process improves resistance to Pitting Corrosion. The time dependence of Corrosion potential and the anodic potential at 1 A·m−2 revealed that the rate of formation of Al oxide films increased due to a decrease in the grain size of the Al after ECAP. Since there exists a negligible amount of impurity precipitates in pure Al, the improvement in Pitting Corrosion resistance of pure Al by ECAP appears to be attributable to an increase in the rate of formation of Al oxide films.
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Effect of Equal Channel Angular Pressing on the Pitting Corrosion Resistance of Aluminum-Copper Alloy
Journal of The Surface Finishing Society of Japan, 2010Co-Authors: In Joon Son, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fukushima, Zenji HoritaAbstract:Effects of equal-channel angular pressing (ECAP) on the Pitting Corrosion resistance of Al-Cu (AA2024) alloy with and without anodization were investigated using surface analysis and polarization curves in solutions containing 300 ppm or 0.6 mol·dm−3 of Cl−. The Pitting Corrosion potential and Corrosion rate of Al-Cu alloy revealed no effect of ECAP on the Pitting Corrosion resistance of Al-Cu. The Al-Cu alloy contained such precipitates as Al2Cu, Al2CuMn and Al-Cu-Si-Fe-Mn intermetallic compounds, around which Pitting Corrosion occurred. Actually, ECAP pulverized these precipitates to decrease their size, but it had no effect on the Pitting Corrosion resistance of Al-Cu alloy because Pitting Corrosion occurred even around small precipitates of Al2Cu. In contrast, the time to initiate Pitting Corrosion of Al-Cu alloy while maintaining a constant potential of 1.2 V was longer with ECAP than without, indicating that ECAP improved the Pitting Corrosion resistance. Although the precipitates of Al2Cu and Al2CuMn disappeared because of oxidation during anodization, Al-Cu-Si-Fe-Mn intermetallic compounds were present and formed defects in anodic oxide films. Pitting Corrosion of the anodized Al-Cu alloy occurred around the Al-Cu-Si-Fe-Mn precipitates. The improved Pitting Corrosion resistance of anodized Al-Cu alloy by ECAP appears to be attributable to the decreased size of the precipitates that initiate Pitting Corrosion.
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Pitting Corrosion resistance of anodized aluminum alloy processed by severe plastic deformation
Materials Transactions, 2008Co-Authors: In Joon Son, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fukushima, Zenji HoritaAbstract:The effect of equal-channel angular pressing (ECAP) on the Pitting Corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L of AlCl3 and also by surface analysis. The time required before initiating Pitting Corrosion of anodized Al-Cu alloy was longer with ECAP than without, indicating improvement in the Pitting Corrosion resistance by application of ECAP. Second phase precipitates were present in Al-Cu alloy matrix and the size of these precipitates was greatly decreased by application of ECAP. The precipitates composed of Si and Al-Cu-Si-Fe-Mn were not oxidized during anodization, and the anodic oxide film were absent at the boundary between the normal oxide films and these impurity precipitates. The Pitting Corrosion of anodized Al-Cu alloy occurred preferentially around these precipitates, the improvement of Pitting Corrosion resistance of anodized Al-Cu alloy by ECAP appears to be attributable to a decrease in the size of precipitates, which act as origins of Pitting Corrosion. [doi:10.2320/matertrans.MRA2008216]
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Effect of equal-channel angular pressing on the Pitting Corrosion resistance of Al alloy
Materials Science Forum, 2006Co-Authors: In Joon Son, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fukushima, Zenji HoritaAbstract:The effect of equal-channel angular pressing (ECAP) on the Pitting Corrosion resistance of Al and Al-Mg alloy was investigated by means of polarization curves in solutions containing 300 ppm of Cl- and by surface analysis. The potentials for Pitting Corrosion of Al and Al-Mg alloy were evidently shifted to the noble direction by using the ECAP process, indicating that this process improves resistance to Pitting Corrosion. This increase in resistance seems to be attributable to the increase in formation rate of Al oxide films due to the increase in grain boundary with ECAP. The Pitting Corrosion resistance of Al and Al-Mg alloy anodized galvanostatically in H2SO4 solution after ECAP was also investigated using electrochemical techniques. The Pitting Corrosion resistance of Al and Al-Mg alloy was remarkably improved by anodizing. However, the Pitting Corrosion resistance of anodized Al-Mg alloy was better without ECAP than with ECAP.
Kazimierz Darowicki - One of the best experts on this subject based on the ideXlab platform.
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Determination of Pitting Corrosion stage of stainless steel by galvanodynamic impedance spectroscopy
Electrochimica Acta, 2017Co-Authors: Juliusz Orlikowski, Agata Jazdzewska, Robert Mazur, Kazimierz DarowickiAbstract:Abstract This paper investigates the methodology for differentiation of multistep process of Pitting Corrosion of AISI 304 stainless steel in the environment of iron (III) chloride. Measurements were performed using Galvanodynamic Electrochemical Impedance Spectroscopy (GDEIS). Application of this methodology allowed monitoring of natural Corrosion process without external current ( I DC = 0A ) nor potential perturbation of the system. Applied sinusoidal AC current does not influence significantly registered DC potential. Analysis confirms that it is possible to distinguish all stages of Pitting Corrosion: passive state, metastable state, initiation of Pitting, active Pitting Corrosion state. Characteristic potential oscillations related with Pitting Corrosion were detected. Research shows that GDEIS method can be with success utilized in the monitoring of Pitting Corrosion.
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Electrochemical and acoustic emission studies of aluminum Pitting Corrosion
Journal of Solid State Electrochemistry, 2009Co-Authors: Stefan Krakowiak, Kazimierz DarowickiAbstract:The potentiodynamic and acoustic emission studies were carried out in a typical three-electrode electrochemical cell. The working electrode was prepared from aluminum alloy 1050A. Cyclic polarization and acoustic emission investigations of Pitting Corrosion were carried out simultaneously. On the basis of acoustic and potentiodynamic (cyclic polarization) investigations Pitting Corrosion potential was determined and compared.
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Detection of random transients caused by Pitting Corrosion
Electrochimica Acta, 2002Co-Authors: Janusz Smulko, Kazimierz Darowicki, A. ZielińskiAbstract:The Corrosion processes can be estimated by measurements of electrochemical noise. Noise can be observed as current and voltage fluctuations in a three-electrode setup. The presence of Pitting Corrosion is manifested as transients in current and voltage fluctuations. For an estimation of the Pitting Corrosion presence in the recorded current fluctuations, the detection of the characteristic transients has been performed. For the determination of transient occurrence, a detection algorithm of the local changes in a spectrogram of the current fluctuations has been used. The spectrogram has been derived using short-time Fourier transform (STFT). The detected transients, characteristic of Pitting Corrosion, have been filtered. A time-varying filtering has been performed using an iterative algorithm, presented in the paper.
Tooru Tsuru - One of the best experts on this subject based on the ideXlab platform.
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Pitting Corrosion of type 430 stainless steel under chloride solution droplet
Corrosion Science, 2010Co-Authors: Sri Hastuty, Atsushi Nishikata, Tooru TsuruAbstract:Abstract To clarify the critical relative humidity (RH) to initiate Pitting Corrosion and the rusting mechanism in a marine atmospheric environment, Pitting Corrosion of Type 430 stainless steels under drops of MgCl 2 solutions were investigated. A Pitting Corrosion test was performed at different relative humidities under droplets with various diameters and thicknesses. The probability of Pitting decreased as the diameter and thickness decreased. Pitting progressed only when the chloride concentration exceeded 4 M, which is the equilibrium concentration at 80% RH. Accordingly, Pitting of Type 430 could be initiated when the RH was less than 80%. Additionally, a Pitting Corrosion mechanism of Type 430 stainless steel under droplets containing chloride ions is proposed.
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Pitting Corrosion mechanism of Type 304 stainless steel under a droplet of chloride solutions
Corrosion Science, 2007Co-Authors: Yusuke Tsutsumi, Atsushi Nishikata, Tooru TsuruAbstract:Abstract Pitting Corrosion of Type 304 stainless steel under drops of MgCl2 solution has been investigated to clarify the rusting mechanism in marine atmospheres. A Pitting Corrosion test was performed under the droplets with various combinations of the diameter and thickness (height) by exposure to a constant relative humidity. Probability of occurrence of Pitting Corrosion decreased with decreasing the diameter and thickness. Pitting Corrosion progressed only when the [Cl−] exceeded 6 M (RH
Wenqiang Li - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Pitting Corrosion monitoring using field signature method
Measurement: Journal of the International Measurement Confederation, 2016Co-Authors: Fangji Gan, Zhengjun Wan, Junbi Liao, Gui Yun Tian, Wenqiang LiAbstract:The field signature method (FSM) is a nondestructive testing (NDT) method based on the potential drop (PD) technique and has been applied to online metal pipe Corrosion monitoring for nearly three decades. The many advantages and benefits of the method have been reported in a number of studies, but few have reported on its limitations or shortcomings. However, the detection accuracy for Pitting Corrosion in FSM is very low. In this paper, the reasons for the low Pitting Corrosion detection accuracy of FSM were analyzed and it was found that different Corrosion pits, which have different sizes, depths or positions, generally have differing influences on the potentials of nearby electrode pairs. Therefore, a new method using a subdivided resistor network to assess Pitting Corrosion is proposed and verified. When compared with the traditional method, the most important parameter, namely the Pitting Corrosion depth detection accuracy, can be significantly improved.
Satoshi Sunada - One of the best experts on this subject based on the ideXlab platform.
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Pitting Corrosion Behavior of Sintered SUS444 Stainless Steel in MgCl2 Solution
Materials Science Forum, 2007Co-Authors: Satoshi Sunada, Yusuke Miyazaki, Kazuhiko MajimaAbstract:The Pitting Corrosion behavior of sintered SUS 444 stainless steels (P/M specimens) with different kinds of porosity ratios of 13.3, 9.11 and 6.88 % was studied in an aqueous solution containing MgCl2 compared with a conventionally processed SUS 444 stainless steel(I/M specimen). The Pitting Corrosion potential decreased almost linearly as porosity ratio increased, and the I/M specimen showed the best resistance against the initiation of Pitting Corrosion. The Pitting Corrosion morphology by SEM observation showed that more small pits were observed on the specimen with larger porosity ratio while less number but larger diameter pits were observed on the specimen with smaller porosity ratio, and it was also confirmed that the I/M specimen had the least number but the largest and deepest pits.
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evaluation of Pitting Corrosion behavior of sintered sus444 stainless steel in mgcl2 solution
Journal of The Japan Society of Powder and Powder Metallurgy, 2004Co-Authors: Satoshi Sunada, Kazuhiko Majima, Yusuke Miyazaki, Takeshi HasegawaAbstract:Three kinds of sintered SUS444 stainless steels (P/M stainless steels) whose porosity ratios were 6.9, 9.1 and 13.3 were used in this experiment, and their Pitting Corrosion behaviors in MgC12 solution were investigated by means of electrochemical measurement and SEM observation compared with normal type SUS444 stainless steel (I/M stainless steel) produced by conventional method. The Pitting Corrosion resistance of P/M stainless steel decreased with the increasing porosity ratio, and it was lower compared with the I/M stainless steel. The potential of Pitting Corrosion decreased with an increase in porosity, and the Pitting Corrosion rate increased as the anodic potential and the porosity ratio increased.
