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Page : 54 - 59
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- The Effect of External DC Electric Field on the Atmospheric Corrosion Behaviour of Zinc under a Thin Electrolyte Layer
- The effect of external DC electric field on atmospheric corrosion behavior of zinc under a thin electrolyte layer (TEL) was investigated by measuring open circuit potential (OCP), cathodic polarization curve, and electrochemical impedance spectroscopy (EIS). Results of OCP vs. time curves indicated that the application
of external DC electric field resulted in a negative shift of OCP of zinc. Results of cathodic polarization curves measurement and EIS measurement showed that the reduction current of oxygen increased while charge transfer resistance (Rct) decreased under the external DC electric field. Variation of OCP negative shift, reduction current of oxygen, and Rct increase with increasing of external DC electric field strength as well as the effect of external DC electric field on double-layer structure in the electrode/electrolyte interface and ions distribution in thin electrolyte layer were analyzed. All results showed that the external DC electric field could accelerate the corrosion of zinc under a thin electrolyte layer. - KEYWORDs : Zinc, Polarization, EIS, Atmosphere corrosion, External DC electric field
- AUTHORs : Qinqin Liang, YanYang, Junxi Zhang†, Xujie Yuan, and Qimeng Chen
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Page : 60 - 67
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- Detection of Iron Phases Presents in Archaeological Artifacts by Raman Spectroscopy
- The compounds associated with corrosion, in metallic archaeological samples of carbon steel of insular origin were evaluated to establish their degree of deterioration and structural damage against air pollution. The iron phases present in samples of archaeological artifacts were detected by Raman spectroscopy and
confocal Raman microcopy. These samples mainly exhibited ing mainly β-FeO(OH) type goethite oxyhydroxides and small amounts of akaganeite α-FeO(OH) lepidocrocite g-FeO(OH) due to dominant chloride in a marine environment and non-stoichiometric oxyhydroxides Fe (II + / III +) as indicators of early corrosion. Some
parts showed the presence of magnetic maghemite indicating high corrosion. g-FeO(OH) is a precursor of phases associated with advanced marine corrosion. By studying its decomposition by Raman spectroscopy, it was synthesized with the following sequence: g-FeO(OH) → α-FeO(OH) + g-FeO(OH), →g?Fe2O3+ Fe3O4.
Ferric compounds provided evidence for the effect of intensity of laser on them, constituting a very useful input for the characterization of oxidation of iron in this type of artifacts. Thus, destructive analysis techniques should be avoided in addition to the use of small amounts of specimen. - KEYWORDs : Iron oxyhydroxides, Marine corrosion, Ferroalloys, Lepidocrocite, Metallic heritage samples
- AUTHORs : A. L. Barbosa†, C. Jimenez, and J. A. Mosquera
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Page : 68 - 73
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- Characterization of Tribocorrosion Behaviour of CoCr Alloy by Electrochemical Techniques in Several Corrosive Media
- Substitution of hip and knee joints by CoCr alloys is in great demand due to their high wear resistance and good biocompatibility. Understanding of tribocorrosion in joint replacements requires study of variables such as coefficient of friction and the choice of a proper corrosive medium in wear-corrosion tests carried out in the lab. The objective of this study was to characterize tribocorrosion behaviour of CoCr
alloy with low (LCCoCr) and high carbon (HCCoCr) contents in several corrosive media: NaCl, Phosphate Buffer Solution (PBS), and PBS with hyaluronic acid (PBS-HA). Tribocorrosion tests were carried out on a pin-on-disk tribometer with an integrated electrochemical cell. A normal load of 5N was applied on the alumina ball counterpart at a rotation rate of 120 rpm. Coefficient of friction (COF) was measured
and tribocorrosion behaviour was characterized by in situ application of electrochemical techniques. HCCoCr alloy immersed in PBS-HA showed the best tribocorrosion behaviour with the lowest COF. In this case, in situ measurement of corrosion potential and the impedance data under wear corrosion process showed an active state while passive film was continuously destroyed without possibility of
regeneration. - KEYWORDs : CoCr alloy, Tribocorrosion, Hyaluronic acid, Electrochemical techniques, Joint
- AUTHORs : M. L. Escudero, I. D?az, J. F. Mart?nez Lerma, R. Montoya, and M. C. Garc?a-Alonso†
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Page : 74 - 80
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- The Biological Functionality of Electro-Galvanized Steels Coated with a Hybrid Composite Containing Pyrethroid
- The electronic industries require environmentally-friendly and highly functional materials to enhance the quality of human life. Home appliances require insect repellent steels that work to protect household microwave ovens from incurring damage by insects such as fire ants and cockroaches in tropical regions. Thus, POSCO has developed new types of functional steels, coated with an array of organic-inorganic hybrid composites on the steel surface, to cover panels in microwave ovens and refrigerators. The composite solution uses a fine dispersion of hybrid solution with polymeric resin, inorganic and a pyrethroid additive in aqueous
media. The hybrid composite solution coats the steel surface, by using a roll coater and is cured using an induction curing furnace on both the continuous galvanizing line and the electro-galvanizing line. The new steels were evaluated for quality performances, salt spray test for corrosion resistance and biological performance for both insect repellent and antimicrobial activity. The new steels with organic-inorganic composite coating exhibit extraordinarily biological functionalities, for both insect repellent and antimicrobial activities for short and long term tests. The composite-coating solution and experimental results are discussed and suggest that the molecular level dispersion of insecticide on the coating layer is key to biological functional performances. - KEYWORDs : Functional coating, Insect repellent, Antimicrobial activity, Galvanized steel
- AUTHORs : Du-Hwan Jo†, Myung-Soo Kim, Jong-Sang Kim, and Hyun-Woo Oh
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Page : 81 - 89
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- Effect of Niobium on Corrosion Fatigue Properties of High Strength Steel
- In this study, the effect of Nb alloying element on the corrosion fatigue properties of high strength steel is investigated by conducting fatigue experiments under corrosive condition and hydrogen induced condition, potentiodynamic polarization test, tensile test and surface analyses. Nb element is added to enhance the mechanical property of medium carbon steel. This element forms MX-type phases such as carbides and
nitrides which are playing an important role in the grain refinement. The grain refinement is one of the effective way to improve mechanical property because both tensile strength and toughness can be improved at the same time. However, MX-type phase precipitates can be a susceptible site to localized corrosion in corrosive environment due to the potential difference between matrix and precipitate. The obtained results showed that Nb-added steel improved corrosion fatigue property by grain refinement. However, it is degraded for hydrogen-induced fatigue property due to Nb, Ti-inclusions acting as a stronger trap. - KEYWORDs : High strength steel, Corrosion fatigue, SEM, Localized corrosion, Inclusion
- AUTHORs : Young-Joo Cho, Sang-Won Cho, and Jung-Gu Kim†
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Page : 91 - 100
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- Anticorrosion Coatings Obtained by Plasma Electrolytic Oxidation on Implant Metals and Alloys
- Development of biodegradable implants for treatment of complex bone fractures has recently become one of the priority areas in biomedical materials research. Multifunctional corrosion resistant and bioactive coatings containing hydroxyapatite Ca10(PO4)6(OH)2 and magnesium oxide MgO were obtained on Mg-Mn-Ce magnesium alloy by plasma electrolytic oxidation. The phase and elemental composition, morphology, and anticorrosion properties of the coatings were investigated by scanning electron microscopy, energy dispersive spectroscopy,
potentiodynamic polarization, and electrochemical impedance spectroscopy. The PEO-layers were post-treated using superdispersed polytetrafluoroethylene powder. The duplex treatment considerably reduced the corrosion rate (>4 orders of magnitude) of the magnesium alloy. The use of composite coatings in inducing bioactivity and controlling the corrosion degradation of resorbable Mg implants are considered promising. We also applied the plasma electrolytic oxidation method for the formation of the composite bioinert coatings on the titanium nickelide surface in order to improve its electrochemical properties and to change the morphological
structure. It was shown that formed coatings significantly reduced the quantity of nickel ions released into the organism. - KEYWORDs : Implant alloys, Protective coating, Plasma electrolytic oxidation, Titanium nickelide
- AUTHORs : S. L. Sinebryukhov†, S. V. Gnedenkov, O. A. Khrisanfova, A. V. Puz’, V. S. Egorkin, and A. G. Zavidnaya
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Page : 101 - 108
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- Effect of Microstructure on the Environmentally Induced Cracking Behavior of Al-Zn-Mg-Cu-Zr Aluminum Alloy
- AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with
multi-stage working operations, and was coated with 10μm thick Al2O3 ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy. - KEYWORDs : Aluminum alloys, Potentiodynamic polarization, Stress corrosion cracking (SCC), Nanomechanical
- AUTHORs : Rahul Ghosh†, A. Venugopal, Pradeep P I, L. Rama krishna, P. Ramesh Narayanan, Bhanu Pant, and Roy M Cherian
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Page : 109 - 115
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- Evaluation of Grooving Corrosion and Electrochemical Properties of H2S Containing Oil/Gas Transportation Pipes Manufactured by Electric Resistance Welding
- Electrical Resistance Welding (ERW) on a longitudinal seam-welded pipe has been extensively used in oil and gas pipelines. It is well known that the weld zone commonly suffers from grooving corrosion in ERW pipes. In this paper, the grooving corrosion performances of API X65 grade non-sour service (steel-A) and API X70 grade sour gas resistant (steel-B) steel electrical resistance welding pipelines were evaluated. The microstructure of the bondline is composed of coarse polygonal ferrite grains and several elongated pearlites. The elongated pattern is mainly concentrated in the center of the welded area. The grooving corrosion test and electrochemical polarization test were conducted to study the corrosion behavior of the given materials. A V-shaped corrosion groove was found at the center of the fusion zone in both the steel-A and steel-B ERW pipes, as the corrosion rate of the bondlines is higher than that of the base metal. Furthermore, the higher volume fraction of pearlite at the bondline was responsible for the higher corrosion rate at the bondline of both types of steel.
- KEYWORDs : Electrical resistance welding, Grooving corrosion, Seam welding, Bondline, API X65
- AUTHORs : Maksudur Rahman, Siva Prasad Murugan, Changwook Ji, Yong Jin Cho, Joo-Yong Cheon, and Yeong-Do Park†
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Page : 116 - 122
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- 증기발생기 전열관 틈새복합환경(Pb+S+Cl)에서 Alloy 690의 응력부식균열거동
- The secondary coolant of a nuclear power plant has small amounts of various impurities (S, Pb, and Cl, etc.) introduced during the initial construction, maintenance, and normal operation. While the concentration of impurities in the feed water is very low, the flow of the cooling water is restricted, so impurities can
accumulate on the Top of Tubesheet (TTS). This environment is chemically very complicated and has a very wide range of pH from acidic to alkaline. In this study, the characteristics of the oxide and the mechanism of stress corrosion cracking (SCC) are investigated for Alloy 690 TT in alkaline solution containing Pb, Cl, and S. Reverse U-bend (RUB) specimens were used to evaluate the SCC resistance. The test solution comprises 3m NaCl + 500ppm Pb + 0.31m Na2SO4 + 0.45m NaOH. Experimental results show that Alloy 690 TT of the crevice environment containing Pb, S, and Cl has significant cracks, indicating that Alloy 690 is vulnerable to stress corrosion cracking under this environment. - KEYWORDs : Lead, SCC, Alloy 690, Corrosion, Crevice Environment
- AUTHORs : Jung-Ho Shin†, Sang-Yeop Lim, and Dong-Jin Kim
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Page : 123 - 128
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- 이온빔을 이용한 표면 미세구조 제어를 통한 발수 표면 제조
- The fabrication of a controlled surface is of great interest because it can be applied to various engineering facilities due to the various properties of the surface, such as self-cleaning, anti-bio-fouling, anti-icing, anti-corrosion, and anti-sticking. Controlled surfaces with micro/nano structures were fabricated using an ion beam focused onto a polypropylene (PP) surface with a fluoridation process. We developed a facile method of fabricating hydrophobic surfaces through ion beam treatment with argon and oxygen ions. The fabrication of low surface energy materials can replace the current expensive and complex manufacturing process. The contact angles (CAs) of the sample surface were 106° and 108° degrees using argon and oxygen ions, respectively. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy were used to determine the chemical composition of the surface. The morphology change of the surfaces was observed by scanning electron microscopy (SEM). The change of the surface morphology
using the ion beam was shown to be very effective and provide enhanced optical properties. It is therefore expected that the prepared surface with wear and corrosion resistance might have a considerable potential in large scale industrial applications. - KEYWORDs : Ion beam irradiation, Surface morphology, Hydrophobic, Contact angle
- AUTHORs : 김동현 · 이동훈†
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