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Page : 151 - 159 DOWNLOAD
Corrosion Monitoring of PEO-Pretreated Magnesium Alloys
The MA8 alloy (formula Mg–Mn–Се) has been shown to have greater corrosion stability than the VMD10
magnesium alloy (formula Mg–Zn–Zr–Y) in chloride-containing solutions by Scanning Vibrating Electrode
Technique (SVET) and by optical microscopy, gravimetry, and volumetry. It has been established that the crucial factor for the corrosion activity of these samples is the occurrence of microgalvanic coupling at the sample surface. The peculiarities of the kinetics and mechanism of the corrosion in the local heterogeneous regions of the magnesium alloy surface were investigated by localized electrochemical techniques. The stages of the corrosion process in artificial defects in the coating obtained by plasma electrolytic oxidation (PEO) at the surface of the MA8 magnesium alloy were also studied. The analysis of the experimental data enabled us to determine that the corrosion process in the defect zone develops predominantly at the magnesium/coating interface. Based on the measurements of the corrosion rate of the samples with PEO and composite polymer-containing coatings, the best anticorrosion properties were displayed by the composite polymer-containing coatings.
KEYWORDs : SVET, PEO, magnesium alloys, composite protective coating, SIET
AUTHORs : A. S. Gnedenkov†, S. L. Sinebryukhov, D. V. Mashtalyar, S. V. Gnedenkov, and V. I. Sergienko

Page : 141 - 150 DOWNLOAD
Status and Prospect of Test Methods of Quality Silicone Water Repellent for Protecting Reinforced Concrete
Impregnating with quality silicone water repellent on the concrete surface is an effective method of protecting concrete. Quality silicone water repellent has been widely used in the engineering profession because of its desirable properties such as hydrophobicity, keeping concrete breathable and preserving the original
appearance of the concrete. The companies in China that produce silicone water repellent are listed. Test methods in the specifications or standards about silicone water repellent in China are summed. The test methods relative to durability of concrete impregnated with silicone water repellent (such as resistant to chloride ion penetration, resistant to alkali, resistance to freezing and thawing and weatherability etc.) and the constructive quality (such as water absorption rate, impregnating depth and the dry velocity coefficient etc.) are compared and analyzed. The results indicate that there are differences among test methods relative to different specifications with the same index and therefore, confusion has ensued when selecting test methods. All test methods with the exception of the method of water absorption rate by using a Karsten flask are not non-destructive methods or conducted in a laboratory. Finally, further research on silicone water repellent during application is proposed.
KEYWORDs : silicone water repellent, reinforced concrete, specification, anticorrosion, silane
AUTHORs : H. Y. Sun†, Z. Y. Yuan, Z. Yang, G. L. Shan, and M. X. Shen

Page : 128 - 140 DOWNLOAD
알루미늄 기지 자동차에 쓰이는 탄소강 리벳과 그라파이트간의 갈바닉 부식 방지 연구
Aluminum alloy matrix may be used for manufacturing lighter automobiles. However, galvanic corrosion may occur between the rivet joint combining aluminum alloy matrix and a CFRP (carbon fiber reinforced plastic) laminate. The possibility of galvanic corrosion may be investigated by measuring galvanic couple currents. Two types of galvanic current measuring methods were used. One method is to use potentiodynamic polarization curves and the other is the ZRA (zero resistance ammeter) method. For galvanic corrosion experiments graphite, a major component of CFRP, was used with carbon steel (rivets) and 6061 aluminum alloys. Regardless of carbon steel, Ni deposited carbon steel, and 316L stainless steels we also investigated the possibility of reduction in galvanic corrosion. Results revealed that even though Ni deposited carbon steel or 316L stainless rivet may slightly increase galvanic current density between those and Al matrix, substitute rivets for carbon steel may be considerably useful for reducing overall galvanic corrosion.
KEYWORDs : galvanic corrosion, graphite, nickel, electrodeposition, SS316L
AUTHORs : 서동일·이재봉†

Page : 115 - 127 DOWNLOAD
국내원전에 매설된 콜타르 코팅 배관의 음극방식과 FEM법을 이용한 방식성능 시뮬레이션
Coal tar-coated pipes buried in a domestic nuclear power plant have operated under the cathodic protection. This work conducted the simulation of the coating performance of these pipes using a FEM method. The pipes, being ductile cast iron have been suffered under considerably high cathodic protection condition beyond
the appropriate condition. However, cathodic potential measured at the site revealed non-protected status. Converting from 3D CAD data of the power plant to appropriate type for a FEM simulation was conducted and cathodic potential under the applied voltage and current was calculated using primary and secondary current distribution and physical conditions. FEM simulation for coal tar-coated pipe without defects revealed over-protection condition if the pipes were well-coated. However, the simulation for coal tar-coated pipes with many defects predict that the coated pipes may be severely degraded. Therefore, for high risk pipes, direct examination and repair or renewal of pipes are strongly recommended.
KEYWORDs : nuclear power plant, coal tar-coated buried pipe, FEM, cathodic protection
AUTHORs : 장현영·김기태·임부택·김경수·김재원·박흥배·김영식†

Page : 109 - 114 DOWNLOAD
Monitoring Cathodic Shielding and Corrosion under Disbonded Coatings
Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday’s law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP,
without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.
KEYWORDs : pipeline, steel, cathodic protection, corrosion monitoring, aqueous solution, electrochemistry
AUTHORs : F. Varela, M. YJ Tan†, B. Hinton, and M. Forsyth

Page : 100 - 108 DOWNLOAD
Corrosion Behavior of High Pressure Die Cast Al-Ni and Al-Ni-Ca Alloys in 3.5% NaCl Solution
In this investigation corrosion behavior of newly developed high-pressure die cast Al-Ni (N15) and Al-Ni-Ca (NX1503) alloys was studied in 3.5% NaCl solution. The electrochemical corrosion behavior was evaluated using open circuit potential (OCP) measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization results validated
that NX1503 alloy exhibited lower corrosion current density (icorr) value (5.969 μA/cm2) compared to N15 (7.387 μA/cm2). EIS-Bode plots revealed a higher impedance (|Z|) value and maximum phase angle value for NX1503 than N15 alloy. Equivalent circuit curve fitting analysis revealed that surface layer (R1) and charge transfer resistance (Rct) values of NX1503 alloy was higher compared to N15
alloy. Immersion corrosion studies were also conducted for alloys using fishing line specimen arrangement to simultaneously measure corrosion rates from weight loss (PW) and hydrogen volume (PH) after 72 hours and NX1503 alloy had lower corrosion rate compared to N15 alloy. The addition of Ca to N15 alloy significantly reduced the Al3Ni intermetallic phase and further grain refinement may be
attributed for reduction in the corrosion rate.
KEYWORDs : aluminum alloys, die-casting, corrosion, polarization, impedance
AUTHORs : Srinivasan Arthanari, Jae Cheol Jang, and Kwang Seon Shin†

Page : 91 - 99 DOWNLOAD
Synergistic Inhibition of Carbon Steel Corrosion by Inhibitor-Blends in Chloride–Containing Simulated Cooling Water
The objective of this work was to develop efficient synergistic inhibitor combinations comprising sodium nitrite (NaNO2) and an inhibitor-blend code named (SN-50), keeping in view of their application in industrial cooling water systems. The electrochemical characteristics of the carbon steel working electrode in simulated
cooling water (SCW), without and with the addition of different combinations of the inhibitors, were investigated using electrochemical impedance spectroscopy (EIS), open circuit potential (OCP). The electrode surface changes were followed by visual characterization methods. It was demonstrated in this study that all the
combinations of the inhibitors exhibited synergistic benefit and higher inhibition efficiencies than did either of the individual inhibitors. The addition of SN-50 inhibitor to the SCW shifted the OCP to more anodic values and increased the polarization resistance (Rp) values of carbon steel at all applied concentrations. The higher the applied sodium nitrite concentration (in the protection concentration range), the higher the obtained Rp values and the inhibition efficiency improved by increasing the inhibitor concentration.
KEYWORDs : inhibition, sodium nitrite, polarization resistance, carbon steel, anodic inhibition
AUTHORs : Abdul Shaban†, Ilona Felhosi, and Gyongyi Vastag

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