한국부식방식학회

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Page : 158 - 169 DOWNLOAD
전해연마 용액에서 안정화 시간과 표면 거칠기에 따른 오스테나이트 스테인리스강의 전기화학적 특성
The objective of this study was to investigate the electrochemical behavior and damage degree of metal surface under different conditions by performing a potentiodynamic polarization experiment using an electropolishing solution for UNS S31603 based on initial delay time and surface roughness (parameters). A second anodic peak occurred at initial delay time of 0s and 100s. However, it was not discovered at 1000s and 3600s. This research referred to an increase in current density due to hydrogen oxidation reaction among various hypotheses for the second anodic peak. After the experiment, both critical current density and corrosion current density decreased when the initial delay time (immersion time) was longer. As a result of surface analysis, characteristics of the potentiodynamic polarization behavior were similar with roughness, although the degree of damage was clearly different. With an increase in surface roughness value, the degree of surface damage was precisely observed. As such, electrochemical properties were different according to the immersion time in the electropolishing solution. To select electropolishing conditions such as applied current density, voltage, and immersion time, 1000s for initial delay time on the potentiodynamic polarization behavior was the most appropriate in this experiment.
KEYWORDs : Electropolishing, Surface roughness, Initial delay time, UNS S31603, Second anodic peak
AUTHORs : 황현규 · 김성종†

Page : 147 - 157 DOWNLOAD
산성비 환경을 모사한 수용액에서 염화물 농도에 따른 전기자동차 배터리 하우징용 재료의 전기화학적 특성 연구
Electrochemical characteristics and damage behavior of 6061-T6 aluminum alloy used as a battery housing material for electric vehicles were investigated in solution simulating the acid rain environment with chloride concentrations. Potentiodynamic polarization test was performed to analyze electrochemical characteristics. Damage behavior was analyzed through Tafel analysis, measurement of damage area, weight loss, and surface observation. Results described that corrosion current density was increased rapidly when chloride concentration excceded 600 PPM, and it was increased about 7.7 times in the case of 1000 PPM compared with 0 PPM. Potentiodynamic polarization experiment revealed that corrosion damage area and mass loss of specimen increased with chloride concentrations. When chloride concentration was further increased, the corrosion damage area extended to the entire surface. To determine damage tendency of pitting corrosion according to chloride concentration, the ratio of damage depth to width was calculated. It was found that the damage tendency decreased with chloride concentrations. Thus, 6061-T6 aluminum alloy damage becomes larger in the width direction than in the depth direction when a small amount of chloride is contained in an acid rain environment.
KEYWORDs : Electric vehicles, Battery housing, 6061-T6 Aluminum alloy, Chloride concentrations, Electrochemical characteristics
AUTHORs : 신동호 · 김성종†

Page : 138 - 146 DOWNLOAD
해수 환경에서 슈퍼 오스테나이트 스테인리스강의 전기화학적 거동에 미치는 캐비테이션 진폭의 영향
The cavitation and potentiodynamic polarization experiments were conducted simultaneously to investigate the effect of cavitation amplitude on the super austenitic stainless steel (UNS N08367) electrochemical behavior in seawater. The results of the potentiodynamic polarization experiment under cavitation condition showed that the corrosion current density increased with cavitation amplitude increase. Above oxygen evolution potential, the current density in a static condition was the largest because the anodic dissolution reaction by intergranular corrosion was promoted. In the static condition, intergranular corrosion was mainly observed. However, damage caused by erosion was observed in the cavitation environment.
The micro-jet generated by cavity collapse destroyed the corrosion product and promoted the repassivation. So, weight loss occurred the most in static conditions. After the experiment, wave patterns were formed on the surface due to the compressive residual stress caused by the impact pressure of the cavity. Surface hardness was improved by the water cavitation peening effect, and the hardness value was the highest at 30 μm amplitude. UNS N08367 with excellent mechanical performance due to its high hardness showed that cavitation inhibited corrosion damage.
KEYWORDs : Super austenitic stainless steel, Cavitation, Seawater, Electrochemical, UNS N08367
AUTHORs : 허호성 · 김성종†

Page : 130 - 137 DOWNLOAD
배열회수보일러 고압 슈퍼히터 튜브 열화도 평가
In this work, the degradation of high-pressure superheater tubes exposed to the flame of a duct burner in a heat recovery steam generator of a district heating system was evaluated. To assess the deterioration of the used superheater tube, the microstructure, microhardness, and tensile properties were investigated by comparison to an unused tube. The study found that a fin bound at the outer surface of the used tube became fragile only in the location facing the flame. This indicates that the tube was directly exposed to the flame from the duct burner or underwent abnormal overheating. While the unused tube showed a uniform value
in hardness and equiaxial grain structure, the used tube revealed a decrease in hardness up to 105 HV and an increase in grain size with a plate-like morphology in the location facing the flame. The coarsening of the grain structure by the flame weakened the mechanical properties of yield strength, tensile strength, and
elongation.
KEYWORDs : Heat recovery steam generator, High-pressure superheater, Degradation, Flame, Overheating
AUTHORs : 송민지 · 최가현1 · 채호병 · 김우철 · 김희산 · 김정구 · 이수열†

Page : 121 - 129 DOWNLOAD
Optimization of Process Parameters for Dry Film Thickness to Achieve Superior Water-based Coating in Automotive Industries
A study on water-based epoxy coated on mild steel using the electroplating method was conducted to optimize the process parameters for dry film thickness to achieve superior paint quality at optimal cost in an automotive plant. The regression model was used to adjust various parameters such as electrode voltage, bath temperature, processing time, non-volatile matter, and surface area to optimize the dry film thickness. The average dry film thickness computed using the model was in the range of 15 – 35 μm. The error in the computed dry film thickness with reference to the experimentally measured dry film thickness value was -0.5809%, which was well within the acceptable limits of all paint shop standards. Our study showed that
the dry film thickness on mild steel was more sensitive to electrode voltage and bath temperature than processing time. Further, the presence of non-volatile matter was found to have the maximum impact on dry film thickness.
KEYWORDs : Surface coating, Regression model, Automobile painting, Dry film thickness, Paint process parameter
AUTHORs : Pranay Kant Prasad, Abhinav Kr Singh, Sandeep Singh, Shailesh Kumar Prasad, and Sudhanshu Shekher Pati†

Page : 111 - 120 DOWNLOAD
Coating Performance of SiO2/ Epoxy Composites as a Corrosion Protector
To solve the corrosion problem of industrial equipment and other constructions containing metals, corrosion protection can be performed by using coating which provides a barrier between the metal and its environment. Coatings play a significant role in protecting irons and steels in harsh marine and acid environments. This study was conducted to identify an anti-corrosive epoxy coating for carbon steel composite with 0.1, 0.3, and 0.5 wt% concentrations of nanoparticles of SiO2 using the dip-coating method. The electrochemical behavior was analyzed with open circuit potential (OCP) technics and polarization curves (Tafle) in 3.5 wt% NaCl and 5 vol% H2SO4 media. The structure, composition, and morphology were characterized using different analytical techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared spectrum (FT-IR), and Scanning Electron Microscopy (SEM). Results revealed that epoxynano SiO2 coating demonstrated a lower corrosion rate of 2.51 × 10-4 mm/year and the efficiency of corrosion protection was as high as 99.77%. The electrochemical measurement showed that the nano-SiO2 / epoxy coating enhanced the anti-corrosive performance in both NaCl and H2SO4 media.
KEYWORDs : Nano silica oxide, Surface modification, Corrosion protection, Metal coating, Anti-corrosion
AUTHORs : Dina R. Rzaij, Nagham Y. Ahmed, and Naseer Alhaboubi†

Page : 100 - 110 DOWNLOAD
Valorization of Cork Waste to Improve the Anti-Corrosion Properties of Concrete Reinforcements
Corrosion of steel reinforcement is the most important mode of concrete structures damages. It strongly depends on the composition and physicochemical properties of the cementitious medium. The use of waste materials as lightweight aggregates in concrete is environmentally recommended in polluted environments such as marine and/or industrial atmospheres in order to reduce its porosity and ensure the requested protection of reinforcing steel. The present study investigated the effect of waste cork addition on corrosion resistance of steel rebar in mortar specimen prepared in the laboratory. The main objective of this study was to improve the corrosion resistance of reinforcing steel. Another objective of this study was to valorize this ecological product and preserve the environment. Results obtained from various electrochemical tests indicated that the presence of a fine cork powder substantially improved the corrosion resistance of steel in the mortar contaminated by chloride ions. This improvement was reflected by a notable decrease in corrosion current density and a shift of corrosion potential of the steel towards more noble values. Moreover, the presence of a fine cork powder in the mortar had no adverse effect on its mechanical properties.
KEYWORDs : Cork, Corrosion, Steel, Concrete, Chlorides
AUTHORs : S. Belkhir, H. Bensabra†, and J. P. Chopart

Page : 89 - 99 DOWNLOAD
A Newly Developed Non-Cyanide Electroless Gold Plating Method Using Thiomalic Acid as a Complexing Agent and 2-Aminoethanethiol as a Reducing Agent
A versatile method for performing non-cyanide electroless gold plating using thiomalic acid (TMA) as a complexing agent and 2-aminoethanethiol (AET) as a reducing agent was investigated. It was found that TMA was an excellent complexing agent for gold. It can be used in electroless gold plating baths at a neutral pH with a high solution stability, makes it a potential candidate to replace conventional toxic cyanide complex. It was found that one gold atomic ion could bind to two TMA molecules to form the [2TMAAu +] complex in a solution. AET can be used as a reducing agent in electroless gold plating solutions. The highest current density was obtained at electrode rotation rate of 250 to 500 rpm based on anodic and cathodic polarization curves with the mixed potential theory. Increasing AET concentration, pH, and temperature significantly increased the anodic polarization current density and shifted the plating potential toward a more negative value. The optimal gold ion concentration to obtain the highest current density was 0.01 M. The cathodic current was higher at a lower pH and a higher temperature. The current density was inversely proportional to TMA concentration.
KEYWORDs : Electroless gold, Non-cyanide gold, Thiomalic acid, 2-Aminoethanethiol
AUTHORs : Jae-Ho Han†, Jae-Bong Lee†, Nguyen Van Phuong, and Dong-Hyun Kim

Page : 77 - 88 DOWNLOAD
Corrosion Protection Effectiveness and Adsorption Performance of Schiff Base-Quinazoline on Mild Steel in HCl Environment
Schiff base quinazoline derivative viz., 3-((2-hydroxy-3-methoxybenzylidene)amino)-2-methylquinazolin-4(3H)-one (SB-Q), was synthesized in this study. Its corrosion protection impact on mild steel (MS) in 1 M hydrochloric acid solution was examined by performing weight loss measurements. The protective efficacy of SB-Q on MS in 1 M HCl was investigated based on its concentrations, immersion period, and immersion temperature. SB-Q was found to be an efficient inhibitor for the corrosion of MS. Its inhibition efficiency was improved by increasing the concentration of SB-Q to an optimal concentration of 500 ppm. Its inhibition efficacy was 96.3% at 303K. Experimental findings revealed that its inhibition efficiency was increased with increasing immersion time, but decreased with an increase in temperature. The adsorption of SB-Q molecules was followed the Langmuir adsorption isotherm model. The adsorption of the examined inhibitor molecules on the surface of mild steel was studied by density functional theory (DFT). DFT investigation confirmed weight loss findings.
KEYWORDs : Corrosion inhibitor, Mild steel, Methylquinazolin, Schiff Base, DFT
AUTHORs : Firas F. Sayyid, Ali M. Mustafa, Mahdi M. Hanoon, Lina M. Shaker, and Ahmed A. Alamiery†

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