한국부식방식학회

Page : 81 - 89 DOWNLOAD
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†

Page : 74 - 80 DOWNLOAD
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

Page : 68 - 73 DOWNLOAD
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. Díaz, J. F. Martínez Lerma, R. Montoya, and M. C. García-Alonso†

Page : 60 - 67 DOWNLOAD
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

Page : 54 - 59 DOWNLOAD
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

Page : 45 - 53 DOWNLOAD
Surface Protection Obtained by Anodic Oxidation of New Ti-Ta-Zr Alloy
A new 80Ti-15Ta-5Zr wt% alloy surface was protected by anodic oxidation in phosphoric acid solution. The protective oxide layer (TiO2, ZrO2 and Ta suboxides and thickness of 15.5 nm) incorporated PO4 3- ions from the solution, according to high resolution XPS spectra. The AFM analysis determined a high roughness with SEM detected pores (20 - 50 nm). The electrochemical studies of bare and anodically oxidized Ti-15Ta-5Zr alloy in Carter-Brugirard saliva of different pH values and saliva with 0.05M NaF, pointed to a nobler surface for the protected alloy, with a thicker electrodeposited oxide layer acting as a barrier against aggressive ions. The oxidized alloy significantly decreased corrosion current densities and total quantity of ions released into the oral environment in comparison with the bare one, at higher polarisation resistance and protective capacity of the electrodeposited layer. The impedance data revealed a bi-layered oxidation film formed by: a dense, compact, barrier layer in contact with the metallic substrate, decreasing the potential gradient across the metal/oxide layer/solution interface, reducing the anodic dissolution and a more permissive, porous layer in contact with the electrolyte. The open circuit potential for protected alloy shifted to nobler values, with thickening of the oxidation
film signifying long-term protection.
KEYWORDs : Ti-15Ta-5Zr alloy, Carter-brugirard saliva, Electrochemical behaviour, AFM, SEM
AUTHORs : C. Vasilescu†, S. I. Drob, J. M. Calderon Moreno, P. Drob, M. Popa, and E. Vasilescu

Page : 37 - 44 DOWNLOAD
Correlation between Carbon Steel Corrosion and Atmospheric Factors in Taiwan
Taiwan has a typical marine climate featuring perennial high-temperature and dampness. This climate, together with the emission of various industrial corrosive waste gases in recent years, contributes a lot to the corrosion of metal materials. In this study, samples of carbon steel exposed to various atmospheres in Taiwan were analyzed to investigate the impacts of atmospheric factors on carbon steel corrosion.
Carbon steel samples were collected from 87 experimental stations between 2009 and 2012. Statistical analysis was employed to investigate the correlations between the carbon steel corrosion situations and the atmospheric factors such as concentrations of sulfur dioxide or chloride, exposure time, rainfall, etc. The results indicate that for samples from industrial areas, the sulfur dioxide concentration and
exposure time during fall and winter are significantly correlated to the condition of the carbon steel corrosion. However, for samples from coastal zones, the significant correlated factors are chloride concentration and wetting time during winter. The results of this study are useful for the development of carbon steel corrosion prediction models.
KEYWORDs : Atmospheric corrosion, Environment factors, Carbon steel, Correlation analysis
AUTHORs : C. M. Lo, L. H. Tsai, C. W. Hu, and M. D. Lin†

메인메뉴

메뉴

하단메뉴