한국부식방식학회

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Benchmarking of Zinc Coatings for Corrosion Protection: A Detailed Characterization of Corrosion and Electrochemical Properties of Zinc Coatings
Due to various types of Zn coatings for many decades for various applications, it is imperative to study and compare their corrosion resistance properties of some of these. Here, we introduce a systematic methodology for evaluation and validation of corrosion protection properties of metallic coatings. According to this methodology, samples are were exposed in an advanced cyclic corrosion test chamber according to ISO 14993, and removed at the end of each withdrawal for respective corrosion and electrochemical characterization to evaluate both barrier and galvanic protection properties. Corrosion protection properties of coatings were evaluated by visual examination according to ISO 10289, mass loss and subsequent corrosion rate measurements, electrochemical properties, and advanced electrochemical scanning techniques. In this study, corrosion protection properties of a commercial zinc rich coating (ZRC) on AISI 1020 mild steel substrates were evaluated and benchmarked against hot dip galvanized (HDG). Results were correlated, and corrosion protection capabilities of the two coatings were compared. The zinc rich coating performed better than hot dip galvanized coating in terms of overall corrosion protection properties, according to the exposure and experimental conditions used in this study. It proved to be a suitable candidate to replace hot dip galvanized coatings for desired applications.
KEYWORDs : steel, zinc coatings, accelerated exposure, corrosion characterization techniques
AUTHORs : Sudesh L Wijesinghe†and Tan Zixi

Page : 31 - 37 DOWNLOAD
Synergistic Effect of Molybdate and Monoethanolamine on Corrosion Inhibition of Ductile Cast Iron in Tap Water
A synergistic effect was observed in the combination of nitrite and ethanolamines. Ethanolamine is one of the representative organic corrosion inhibitors and can be categorized as adsorption type. However, nitrosamines can form when amines mix with sodium nitrite. Since nitrosamine is a carcinogen, the co-addition of nitrite and ethanolamine will be not practical, and thus, a non-toxic combination of inhibitors shall be needed. In order to maximize the effect of monoethanolamine, we focused on the addition of molybdate. Molybdate has been used to alternate the addition of chromate, but it showed insufficient oxidizing power relative to corrosion inhibitors. This work evaluated the synergistic effect of the co-addition of molybdate and monoethanolamine, and its corrosion mechanism was elucidated. A high concentration of molybdate or monoethanolamine was needed to inhibit the corrosion of ductile cast iron in tap water, but in the case of the co-addition of molybdate and monoethanolamine, a synergistic effect was observed. This synergistic effect could be attributed to the molybdate that partly oxidizes the metallic surface and the monoethanolamine that is simultaneously adsorbed on the graphite surface. This adsorbed layer then acts as the barrier layer that mitigates galvanic corrosion between the graphite and the matrix.
KEYWORDs : ductile cast iron, corrosion inhibitor, molybdate, ethanolamine, synergistic effect
AUTHORs : K. T. Kim, H. Y. Chang, B. T. Lim, H. B. Park, and Y. S. Kim†

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Hydrodynamic Effect on the Inhibition for the Flow Accelerated Corrosion of an Elbow
The inhibition effect of thioureido imidazoline inhibitor (TAI) for flow accelerated corrosion (FAC) at different locations for an X65 carbon steel elbow was studied by array electrode and computational fluid dynamics (CFD) simulations. The distribution of the inhibition efficiency measured by electrochemical impedance spectroscopy (EIS) is in good accordance with the distribution of the hydrodynamic parameters at the elbow. The inhibition efficiencies at the outer wall are higher than those at the inner wall meaning that the lower inhibition efficiency is associated with a higher flow velocity, shear stress, and turbulent kinetic energy at the inner wall of the elbow, as well as secondary flow at the elbow rather than the mass transport of
inhibitor molecules. Compared to the static condition, the inhibition efficiency of TAI for FAC was relatively low. It is also due to a drastic turbulence flow and high wall shear stress during the FAC test, which prevents the adsorption of inhibitor and/or damages the adsorbed inhibitor film.
KEYWORDs : carbon steel, elbow, flow accelerated corrosion (FAC), thioureido imidazoline inhibitor (TAI), computational fluid dynamics (CFD) simulation
AUTHORs : L. Zeng, G. A. Zhang†, and X. P. Guo

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Effects of Oxygen Partial Pressure on Oxidation Behavior of CMnSi TRIP Steel in an Oxidation-Reduction Scheme
An oxidation-reduction scheme is an alternative approach for improving the galvanizability of advanced high-strength steel in the continuous hot-dip galvanizing process. Here, we investigated the effect of oxygen partial pressure (PO2) on the oxidation behavior of a transformation-induced plasticity steel containing 1.5 wt% Si and 1.6 wt% Mn during heating to and holding for 60 s at 700 °C under atmospheres with various PO2 values. Irrespective of PO2, a thin amorphous Si-rich layer of Si-Mn-O was formed underneath the Fe oxide scale (a Fe2O3/Fe3O4 bilayer) in the heating stage. In contrast to Si, Mn tended to segregate at the scale surface as (Fe,Mn)2O3. The multilayered structure of (Fe,Mn)2O3/Fe2O3/Fe3O4/amorphous Si-Mn-O remained even after extended oxidizing at 700 °C for 60 s. Fe2O3 was the dominantly growing oxide phase in the scale. The enhanced growth rate of Fe2O3
with increasing PO2 resulted in the formation of more Kirkendall voids in the amorphous Si-rich layer and a less Mn segregation at the scale surface. The mechanisms underlying the absence of FeO and the formation of Kirkendall voids are discussed.
KEYWORDs : oxidation, transformation-induced plasticity steel, oxidation-reduction scheme, oxygen partial pressure, amorphous Si oxide
AUTHORs : Seong-Hwan Kim, Joo-Youl Huh†, Myung-Soo Kim, and Jong-Sang Kim

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Corrosion Behavior and Oxide Film Formation of T91 Steel under Different Water Chemistry Operation Conditions
The corrosion behavior of a ferritic/martensitic steel T91 exposed to an aqueous solution containing chloride and sulfate ions is investigated depending on the stimulated all-volatile treatment (AVT) and under oxygenated treatment (OT) conditions. The corrosion of T91 steel under OT condition is severe, while the corrosion under AVT condition is not. The co-existence of chloride and sulfate ions has antagonistic effect on the corrosion of T91 steel in both AVT and OT conditions. Unlike to corrosion resistance in the aqueous solution, OT pretreatment provides T91 steel lower oxidation-resistance than VAT pretreatment. From scanning electron
microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis, the lower corrosion resistance in the aqueous solution by VAT conditions possibly is due to the formation of pits. In addition, the lower oxidation resistance of T91 steel pretreated by OT conditions is explained as follows: the cracks formed during the immersion under OT conditions accelerated peeling-off rate of the oxide film.
KEYWORDs : T91 steel, oxidation, corrosion, electric power plant
AUTHORs : D. Q. Zhang†, C. Shi, J. Li, L. X. Gao, and K. Y. Lee

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Use of Local Electrochemical Methods (SECM, EC-STM) and AFM to Differentiate Microstructural Effects (EBSD) on Very Pure Copper
When aiming for an increased and more sustainable use of metals a thorough knowledge of the corrosion phenomenon as function of the local metal microstructure is of crucial importance. In this work, we summarize the information presented in our previous publications[1-3] and present an overview of the different local (electrochemical) techniques that have been proven to be effective in studying the relation between different microstructural variables and their different electrochemical behavior. Atomic force microscopy (AFM)[1], scanning electrochemical microscopy (SECM)[2], and electrochemical scanning tunneling microscopy (EC-STM)[3] were used in combination with electron backscatter diffraction (EBSD). Consequently, correlations could be identified between the grain orientation and grain boundary characteristics, on the one hand, and the electrochemical behavior on the other hand. The grain orientation itself has an influence on the corrosion, and the orientation of the neighboring grains also seems to play a decisive role in the dissolution rate. With respect to intergranular corrosion, only coherent twin boundaries seem to be resistant.
KEYWORDs : copper, microstructure, EBSD, EC-STM, AFM, SECM
AUTHORs : Esther Martinez-Lombardia, Linsey Lapeire, Vincent Maurice, Iris De Graeve, Lorena Klein, Philippe Marcus, Kim Verbeken, Leo Kestens, Yaiza Gonzalez-Garcia, Arjan Mol, and Herman Terryn†

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Erratum to: An Overview of New Progresses in Understanding Pipeline Corrosion
An approach to achieving the ambitious goal of cost effectively extending the safe operation life of energy pipeline to 100 years is the application of health monitoring and life prediction tools that are able to provide both long-term remnant pipeline life prediction and in-situ pipeline condition monitoring. A critical step is the enhancement of technological capabilities that are required for understanding and quantifying the effects of key factors influencing buried steel pipeline corrosion and environmentally assisted materials degradation, and the development of condition monitoring technologies that are able to provide in-situ monitoring and site-specific warning of pipeline damage. This paper provides an overview of our current research aimed at developing new sensors and electrochemical cells for monitoring, categorising and quantifying the level and nature of external pipeline and coating damages under the combined effects of various inter-related variables and processes such as localised corrosion, coating cracking and disbondment, cathodic shielding, transit loss of cathodic protection.
KEYWORDs : pipeline life prediction, corrosion monitoring, oil & gas pipeline, protective coatings, cathodic protection
AUTHORs : M. YJ Tan†, F. Varela, Y. Huo, R. Gupta, D. Abreu, F. Mahdavi, B. Hinton, and M. Forsyth

Page : 0 - 0 DOWNLOAD
Erratum to: The Effect of Improved Crosslink Density on the Properties of Waterborne Polyurethanes Using Sol-Gel Process
Water-based systems are dominating the coating market because of worldwide VOCs regulations. Research is focusing especially on waterborne polyurethane (WPU) because of its unique mechanical and chemical properties. However, commercial WPU consists of linear thermoplastic polymers with polar groups on the main chain, which do not perform as well as solvent-borne PU in a two-pack system. In this study, APTES were used as a chain crosslink agent to overcome commercial WPU’s limited performance. WPUs synthesized by using a sol-gel process were evaluated with FT-IR, particle analysis, TGA, tensile tests, pull-off tests, SEM, and EIS. The results showed that WPUs with added APTES had better thermal stability, mechanical properties, and water resistance than did WPUs without
added APTES. Consequently, the sol-gel process increased the crosslink density of WPUs and modified the WPU’s own properties.
KEYWORDs : waterborne polyurethane, sol-gel, crosslink density, EIS, water uptake
AUTHORs : Young Ryul Kim and Jin Hwan Park†

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