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Page : 64 - 72
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- 치과용 Ni-Ti합금의 표면특성에 미치는 Mo함량의 영향
- Ni-Ti shape memory alloy for dental nerve treatment devices was prepared by adding Mo to Ni-Ti alloy to improve flexibility and fatigue fracture characteristics and simultaneously increase corrosion resistance. Surface properties of the alloy were evaluated. Microstructure analysis of the Ni-Ti-xMo alloy revealed that the amount of needle-like structure increased with increasing Mo content. The shape of the precipitate showed a pattern in which a long needle-like structure gradually disappeared and changed into a small spherical shape. As a result of XRD analysis of the Ni-Ti-xMo alloy, R-phase structure appeared as Mo was added. R-phase and B2 structure were mainly observed. As a result of DSC analysis, phase transformation of the Ti-Ni-Mo alloy showed a twostep phase change of B2-R-B19\' transformation with two exothermic peaks and one endothermic peak. As Mo content increased, R-phase formation temperature gradually decreased. As a result of measuring surface hardness of the Ti-Ni-Mo alloy, change in hardness value due to the phase change tended to decrease with increasing Mo content. As a result of the corrosion test, the corrosion potential and pitting potential increased while the current density tended to decrease with increasing Mo content.
- KEYWORDs : Ni-Ti file, Shape memory alloy, R-phase, Corrosion resistance, Ni-Ti-Mo alloy
- AUTHORs : 최한철†·김재운·박순균
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Page : 73 - 89
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- Gravimetric Measurements and Theoretical Calculations of 4-Aminoantipyrine Derivatives as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution: Comparative Studies
- Due to continuous promotion of green alternatives to toxic petrochemicals by government policies,
research efforts towards the development of green corrosion inhibitors have intensified recently. The objective of the current work was to develop novel green and sustainable corrosion inhibitors derived from 4-aminoantipyrine to effectively prevent corrosion of mild steel in corrosive environments. Gravimetric methods were used to investigate corrosion inhibition of 4-((furan-2-ylmethylene)amino)antipyrine (FAP) and 4-((pyridin-2-ylmethylene)amino)antipyrine (PAP) for mild steel in 1 M HCl. FAP and PAP were subjected to quantum chemical calculations using density functional theory (DFT). DFT was used to determine the mechanism of mild steel corrosion inhibition using inhibitors tested in HCl. Results demonstrated that these tested inhibitors could effectively inhibit mild steel corrosion in 1.0 M HCl. At 0.0005 M, these inhibitors’ efficiencies for FAP and PAP were 93.3% and 96.5%, respectively. The Langmuir adsorption isotherm was obeyed by these inhibitors on the mild steel surface. Values of adsorption free energies, ??G?_ads^o, revealed that FAP followed chemical and physical adsorptions. - KEYWORDs : 4-Aminoantipyrine, Furan, Pyridine, Corrosion inhibitor, Gravimetric
- AUTHORs : Firas F. Sayyid, Ali M. Mustafa, Slafa I. Ibrahim, Mustafa K. Mohsin, Mahdi M. Hanoon, Mohammed H. H. Al-Kaabi, A. A. H. Kadhum, Wan Nor Roslam Wan Isahak, and A. A. Al-Amiery†
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Page : 90 - 98
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- Corrosion Protection Properties of Co3O4 and CoFe2O4 Nanoparticles for Water-Based Epoxy Coatings on 2024-T3 Aluminum Alloys
- In this study, cobalt oxide (Co3O4) and cobalt-doped magnetite (CoFe2O4) nanoparticles were synthesized by a hydrothermal method. They were then used as corrosion inhibitors for corrosion protection of AA2024-T3 aluminum alloys. These obtained nanoparticles were characterized by x-ray diffraction, fieldemission scanning electron microscopy, and Zeta potential measurements. Corrosion inhibition activities of Co3O4 and CoFe2O4 nanoparticles were determined by performing electrochemical measurements for bare AA2024-T3 aluminum alloys in 0.05 M NaCl + 0.1 M Na2SO4 solution containing Co3O4 or CoFe2O4 nanoparticles. Corrosion protection for AA2024-T3 aluminum alloys by a water-based epoxy with or without the synthesized Co3O4 or CoFe2O4 nanoparticles was investigated by electrochemical impedance spectroscopy during immersion in 0.1 M NaCl solution. The corrosion protection of epoxy coating deposited on the AA2024-T3 surface was improved by incorporating Co3O4 or CoFe2O4 nanoparticles in the coating. The corrosion protection performance of the epoxy coating containing CoFe2O4 was higher than that of the epoxy coating containing Co3O4.
- KEYWORDs : Aluminum alloy, Cobalt oxide nanoparticle, Cobalt-doped magnetite, Corrosion inhibition, EIS
- AUTHORs : Thu Thuy Thai†, Anh Truc Trinh†, Thi Thanh Tam Pham, and Hoan Nguyen Xuan
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Page : 99 - 107
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- Incorporation of Montmorillonite/Silica Composite for the Corrosion Protection of an Epoxy Coating on a 2024 Aluminum Alloy Substrate
- Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.
- KEYWORDs : AA5083-H321, Electrochemical experiment, Natural seawater, Sacrificial anode protection
- AUTHORs : Thai Thu Thuy, Trinh Anh Truc†, and Pham Gia Vu
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Page : 108 - 114
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- 알루미늄 열용사 코팅된 AA5083-H321의 내식성 평가
- In this study, anti-corrosion effect was investigated through various electrochemical experiments after applying Al thermal spraying technology to AA5083-H321. Open circuit potential and anodic polarization curves were analyzed through electrochemical experiments in natural seawater. The shape of the surface was observed using a scanning electron microscope (SEM) and a 3D microscope before and after the experiment. Component and crystal structure were analyzed through EDS and XRD. As a result, the surface roughness of AA5083-H321 and the Al thermal sprayed coating layer increased due to surface damage caused by anodic dissolution reaction during the anodic polarization experiment. The corrosion rate of AA5083-H321 was relatively low because the Al thermal spray coating layer contained structural defects such as pores and crevices. Nevertheless, the open circuit potential of the Al thermal spray coating layer in natural seawater was measured about 0.2 V lower than that of AA5083-H321. Thus, a sacrificial anode protection effect can be expected.
- KEYWORDs : AA5083-H321, Electrochemical experiment, Natural seawater, Sacrificial anode protection
- AUTHORs : 박일초 · 김성준 · 한민수†
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Page : 115 - 122
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- 열수송관에 연결된 에어벤트에 적용 가능한 부식 방지 방안
- This study aimed to elucidate causes of corrosion of heat transport pipes and air vents installed under a manhole of heat transport facilities and suggest effective anticorrosive measures by applying paints or adhesive tapes. It was found that air vent corrosion was attributed to corrosion under insulation caused by the inflow of water and the enrichment of chloride ions. The infiltrated water caused a hydrolysis of polyurethane foam (PUF) insulation by concentrating chloride ions at the interface between a pipe and the PUF. As insulator deteriorated, more chloride ions were eluted as confirmed by ion chromatograph (IC) analysis. As an effective method to prevent air vent corrosion, different types of paints and adhesive tapes with higher corrosion resistance on chloride ions were applied and environmental resistance tests were performed with those samples. Based on environmental test results of samples exposed to 10% HCl solution, it was revealed that a wax tape was the most adequate from a viewpoint of stability at operating condition, environmental resistance, surface treatment, and field applicability.
- KEYWORDs : District heating system, Air vent, Corrosion, Chloride ion, Adhesive tapes
- AUTHORs : 송민지 · 최가현 · 김우철 · 이수열†
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Page : 123 - 130
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- 플랜트팜용 3원계 (Zn-Al-Mg) 합금도금 강판의 국부손상에 따른 부식 메커니즘
- This study aimed to evaluate corrosion resistance of steel coated with GI and Zn-Al-Mg alloy using cyclic corrosion test (CCT) with electrochemical polarization and impedance measurements. Results showed that the Zn-Al-Mg alloy coated steel had a much higher corrosion rate than GI coated steel in early stages of corrosion. With prolonged immersion, however, the corrosion rate of the Zn-Al-Mg alloy coated steel greatly decreased, mainly owing to a significant decrease in the cathodic reduction reaction and an increase in polarization resistance at the surface. This was closely associated with the formation of protective corrosion products including Zn5(OH)8Cl2·H2O and Zn6Al2(OH)16CO3. Moreover, when the steel substrate was locally exposed due to mechanical damage, the kinetics of anodic dissolution from the coating layer and the formation of protective corrosion products on the surface of the Zn-Al-Mg alloy coated steel became much faster compared to the case of GI coated steel. This could provide a longer-lasting corrosion inhibition function for Zn-Al-Mg alloy coated steel used in plant farms.
- KEYWORDs : Zn-Al-Mg, Hot-dip galvanized steel, Corrosion, Localized damage, Electrochemical polarization test
- AUTHORs : 박진성 · 이재원 · 김성진†
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Page : 131 - 136
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- 고강도강의 미세조직 제어가 수소확산계수, 트랩 활성화에너지 및 Sour 환경 내 균열 저항성에 미치는 영향
- The aim of this study was to investigate effects of microstructure control on hydrogen diffusivity, trap activation energy, and cracking behaviors of high-strength steel using a range of experimental techniques. Results of this study showed that susceptibility to hydrogen induced cracking (HIC) was significantly associated with hydrogen diffusivity and trap activation energy, which were primarily influenced by the microstructure. On the other hand, microstructural modifications had no significant impact on electrochemical polarization behavior on the surface at an early corrosion stage. To ensure high resistance to HIC of the steel, it is recommended to increase the cooling rate during normalizing to avoid formation of banded pearlite in the microstructure. However, it is also essential to establish optimal heat treatment conditions to ensure that proportions of bainite, retained austenite (RA), and martensite-austenite (MA) constituents are not too high. Additionally, postheat treatment at below A1 temperature is desired to decompose locally distributed RA and MA constituents.
- KEYWORDs : Microstructure, Hydrogen embrittlement, H2S, Corrosion
- AUTHORs : 박진성 · 김성진†
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Page : 137 - 152
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- Polarization Behavior and Corrosion Inhibition of Copper in Acidic Chloride Solution Containing Benzotriazole
- Polarization behavior and corrosion inhibition of copper in acidic chloride solutions containing benzotriazole were studied. Pourbaix diagrams constructed for copper in NaCl solutions with different BTAH concentrations were used to understand the polarization behavior. Open circuit potential (OCP) depended not only on chloride concentration, but also on whether a CuBTA layer was formed on the copper surface. Only when the (pH, OCP) was located well in the CuBTA region of the Pourbaix diagram, a stable corrosion inhibiting CuBTA layer was formed, which was confirmed by X-ray Photoelectron Spectroscopy (XPS) and a long-term corrosion test. The OCP for the CuBTA layer decreased logarithmically with increasing [Cl-] activity in the solution. A minimum BTAH concentration required to form a CuBTA layer for a given NaCl concentration and pH were determined from the Pourbaix diagram. It was found that 320 ppm BTAH solution could be used to form a corrosion-inhibiting CuBTA layer inside the corrosion pit in the sprinkler copper tube, successfully reducing water leakage rate of copper tubes. These experimental results could be used to estimate water chemistry inside a corrosion pit.
- KEYWORDs : Benzotriazole, Copper, Chloride, Polarization, Pourbaix diagram
- AUTHORs : Sang Hee Suh† and Youngjoon Suh
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Page : 153 - 163
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- Difference of Potential Range Formed at the Anode Between Water Drop Test and Temperature Humidity Bias Test to Evaluate Electrochemical Migration of Solders for Printed Circuit Board
- Two types of accelerated tests, Water Drop Test (WDT) and Temperature-Humidity-Bias Test (THBT), can be used to evaluate the susceptibility to electrochemical migration (ECM). In the WDT, liquid water is directly applied to a specimen, typically a patterned conductor like a printed circuit board. Time to failure in the WDT typically ranges from several seconds to several minutes. On the other hand, the THBT is conducted under elevated temperature and humidity conditions, allowing for assessment of design and life cycle factors on ECM. THBT is widely recognized as a more suitable method for reliability testing than WDT. In both test methods, localized corrosion can be observed on the anode. Composition of dendrites formed during the WDT is similar to that formed during THBT. However, there is a lack of correlation between the time to failure obtained from WDT and that obtained from THBT. In this study, we investigated the relationship between electrochemical parameters and time to failure obtained from both WDT and THBT. Differences in time to failure can be attributed to actual anode potential obtained in the two tests.
- KEYWORDs : Printed circuit board, Solder, Electrochemical Migration, Pitting potential, Protection potential
- AUTHORs : Young Ran Yoo and Young Sik Kim†
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