• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.17-17
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• 2012

Magnesium alloys exhibit many attractive properties such as low density, high strength/weight ratio, high thermal conductivity, very good electromagnetic features and good recyclability. However, most commercial magnesium alloys require protective coatings because of their poor corrosion resistance. Attempts have been made to improve the corrosion resistance of the Mg alloys by surface treatments, such as chemical conversion coatings, anodizing, plating and metal coatings, are commonly applied to magnesium alloys in order to increase the corrosion resistance. Among them, chemical conversion coatings are regarded as one of the most effective and cheapest ways to prevent corrosion resistance. In this study, zinc phosphate conversion coatings on various Mg alloys have been developed by selecting proper phosphating bath composition and concentration and by optimizing phosphating time, temperature. Morphology, coatings composition, corrosion resistance, adhesion and its formation and growth mechanism of the zinc phosphate conversion coatings were studied. Results have shown some attractive properties such as simplicity in operation, significantly increased corrosion protective property. However, adhesions between coatings and substrate and also between coatings and paint are still not satisfied. Resolving the problems and understanding the mechanism of phosphating process are targets of our study.

• Corrosion Science and Technology
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• 제19권2호
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• pp.57-65
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• 2020

As competition among global automakers intensifies, demand for materials that are better in price and performance is increasing. While steel and plastic materials compete for automotive fuel tanks, plastic materials have advantages such as light weight for automobiles. However, they have high prices. Accordingly, in this paper, four types of Zn-X plated steel sheets, electroplating (X = none, Sn) and galvannealed (X = Fe, Fe-Mg), were manufactured and their applicability as a fuel tank material was evaluated. Nano-composite coating solution with good conductivity was treated on the surface of plated steels using a roll coater and then cured through induction furnace to improve corrosion resistance. Quality characteristics such as corrosion resistance, fuel resistance to diverse gasoline and diesel fuels, and seam weldability were evaluated for the above plated steels. Their properties were compared and analyzed with conventional Zn-Ni electroplating steels. Among the above plated steels, Zn-Fe-Mg galvannealed steels coated with nano-composite coating exhibited better properties than other steels. Detailed experimental results suggest that evenly distributed Mg elements on the coating layer play a key role in the enhanced quality performance.

• Corrosion Science and Technology
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• 제13권5호
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• pp.170-177
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• 2014

Polyurethane coating was designed to give a hydrophobic property on its surface by modifying it with hydroxyl terminated polydimethylsiloxane and then effects of surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified polyurethane coating were examined using FT-IR/ATR spectroscopy, contact angle measurement and electrochemical impedance test. As results, the surface of polyurethane coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between polyurethane and modifier by the modification. The phase separation tendency is more appreciable when modified by polydimethylsiloxane with higher content. Water transport behavior of the modified polyurethane coating decreased more in that with higher hydrophobic surface property. The decrease in the impedance modulus ${\mid}Z{\mid}$ at low frequency region in immersion test for polyurethane coatings was associated with the water transport behavior and surface hydrophobic properties of modified polyurethane coatings. The corrosion protectiveness of the modified polyurethane coated carbon steel generally increased with an increase in the modifier content, confirming that corrosion protectiveness of the modified polyurethane coating is well agreed with its water transport behavior.

• Corrosion Science and Technology
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• 제10권3호
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• pp.95-100
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• 2011

Protective coatings play an important role in the protection of metallic structures against corrosive environment. The main function of anticorrosive coating is to prevent the materials from corrosive agents, such as water, oxygen and ions. In the study, the corrosion protection properties of urethane and epoxy coating systems were evaluated using EIS methods exposed to the corrosion acceleration test such as Norsok M501, Prohesion and hygrothermal cyclic test. AFM analysis of the coating systems was carried out to monitor the change of roughness of coatings. Urethane coating system was more stable than the epoxy coating under given cyclic conditions. Water uptake into the urethane coatings was less than that into the epoxy coating. The urethane coating system showed better corrosion protection than epoxy coating system based on the changes of the impedance modulus at low frequency region with exposure time. Consequently, the corrosion protection properties of the epoxy and urethane coatings was well correspond with their surface roughness changes and water uptakes.

• 대한치과기공학회지
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• 제30권2호
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• pp.9-16
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• 2008

The surface microstructural changes, mechanical properties and corrosion resistance of Ti-Pd alloys for dental biomaterials have been investigated. Ti, Ti-Pd alloys were melted in arc furnace and the corrosion resistance of Ti-Pd alloys was evaluated by anodic polarization test. The surface microstructural changes and mechanical properties of Ti-Pd alloys were analysed by scanning electron microscope and Vickers micro-hardness tester. The vickers hardnees of pure Ti improved by addition of Pd but Ti-25Pd alloy showed decreasing compared with Ti-15Pd. And anodic polarization and potentiostatic test were conducted in 5% HCl to quantify the resistance to corrosion with the addition of Pd, There was no significant difference in corrosion resistance between pure Ti, Ti-5Pd and Ti-15Pd alloy. However, Ti-25Pd alloy showed decreasing compared with pure Ti in corrosion resistance. From these results, it was concluded that newly formulated Ti-15Pd experimental alloy have adequate hardness and high corrosion resistance, and this alloy is promising candidate for a successful dental casting alloy.

• 한국표면공학회지
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• 제54권4호
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• pp.194-199
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• 2021

In this study, rebar corrosion detection sensor was fabricated using multi-walled carbon nanotubes (MWCNTs). MWCNTs were pre-treated in the acid electrolytes to attach the carboxylic acid to the surface of MWCNTs. The fabricated sensor was attached on the surface of rebar and it detected the corrosion of steel using LCR meter with variation of capacitance. The surface morphology and electrical properties were characterized using scanning electron microscope (SEM) and electrical test equipment, respectively. To verify the corrosion detection characteristics, comparison experiment using plastic bar was performed. Moreover, mechanism of corrosion detection sensor was discussed.

• 한국표면공학회지
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• 제54권1호
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• pp.12-17
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• 2021

Among the various precious metals, silver is used in various fields because of its low price than other precious metals. However, the surface of silver remains after rain in the atmosphere containing sulfur ions and chlorine ions, causing silver corrosion and discoloration. Existing documents have developed a anode to prevent corrosion but that are concentrated on secondary batteries. This study tried to prevent corrosion and discoloration of silver by using an Al sacrificial anode. Sulfuric acid decreased the potential of silver and increased the current density at active polarization and OCP. The amount of corrosion of silver with the Al sacrificial anode was reduced from 0.5 % to 6.5%. When silver is used for decoration outside, corrosion and discoloration of silver can be suppressed by installing an Al anode.

• 대한금속재료학회지
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• 제50권9호
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• pp.619-627
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• 2012

One of the barriers limiting wide applications of magnesium alloys to various industries is their poor corrosion resistance. The corrosion properties of AZ91 magnesium alloy, which is the most popular magnesium casting alloy, are affected by microstructural and environmental factors. The corrosion properties of AZ91 magnesium alloy are affected by the corrosion properties of ${\alpha}-Mg$ and ${\beta}$ phases, the volume fraction and distribution of ${\beta}$ phase and area ratio of ${\alpha}-Mg/{\beta}$ phases. The corrosion properties of AZ91 magnesium alloy under various environments also change according to the passivity of films and types of corrosion products formed on its surface. The corrosion resistance of the magnesium alloys can be improved by microstructural control through the addition of alloying elements and optimization of the production process.

• Corrosion Science and Technology
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• 제23권1호
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• pp.20-32
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• 2024

Metal corrosion in acidic environments is a major issue in various industrial applications. This study evaluates the 4-piperonylideneaminoantipyrine (PPDAA) corrosion inhibition efficiency for mild steel in a hydrochloric acid (HCl) solution. The weight loss method was used to determine the corrosion inhibition efficiency at different concentrations and immersion time periods. Results revealed that the highest inhibition efficiency (94.3%) was achieved at 5 mM concentration after 5 hours of immersion time. To inspect the surface morphology of the inhibitor film on the mild steel surface, scanning electron microscopy (SEM) was used before and after immersion in 1.0 M HCl. Density functional theory (DFT) calculations were performed to investigate the molecular structure and electronic properties of the inhibitor molecule to understand the corrosion inhibition mechanism. Theoretical results showed that the inhibitor molecule can adsorb onto the mild steel surface through its nitrogen and oxygen atoms, forming a protective layer that prevents HCl corrosive attack. These findings highlight the potential of PPDAA as an effective corrosion inhibitor for mild steel in HCl solution. Moreover, combining experimental and theoretical approaches provides insights into the mechanism of corrosion inhibition, which is essential for developing effective strategies to prevent metal corrosion in acidic environments.

• 한국압력기기공학회 논문집
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• 제20권1호
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• pp.16-24
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• 2024

Denting of steam generator (SG) tube is defined as the reduction in tube diameter due to the stresses exerted by the corrosion products formed on the outer diameter surface. This phenomenon is mostly observed in the crevices between SG tube and the top-of tubesheet or tube support plate. Despite the replacement of SG tube with Alloy 690, which has better corrosion resistance than Alloy 600, the denting of SG tube still remains a potential problem that could decrease the SG integrity. Deformation of SG tube by denting phenomenon can affect the surface properties and microstructure of SG tube. In this study, the effects of plastic deformation on surface properties and microstructure of Alloy 690 thermally treated (TT) tube was investigated by using the various analysis techniques. The plastic deformation of Alloy 690 increased the surface roughness and area. Many surface defects such as ripped surface and micro-cracks were observed on the deformed Alloy 690TT specimen. Based on the electron backscatter diffraction analysis, the dislocation density of deformed SG tube increased compared to non-deformed SG tube. In addition, the effects of changes in surface properties and microstructure of SG tube on general corrosion behavior were discussed.