• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2742-2746
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• 2023

The corrosion behavior of copper immersed in dilute oxychloride solution (100 mM) was studied through surface investigation and in-situ monitoring of open-circuit potential. The copper corrosion was initiated with copper dissolution into a form of CuCl^-₂, resulting in mass decrease within the first 40 h of immersion. This was followed by a hydrolysis reaction initiated by the CuCl^-₂ at the copper surface, after which oxide products were formed and deposited on the surface, resulting in a mass increase. The formation of nucleation sites for copper oxide and its lateral extension during the corrosion process were examined using focused ion beam (FIB)-scanning electron microscopy (SEM). The presence of metastable compounds such as atacamite (CuCl₂·3Cu(OH)₂) on the corroded copper surface was revealed by X-ray photoelectron spectra (XPS) and transmission electron microscopy (TEM)-energy dispersive spectrometry (EDS) analysis.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.137-152
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• 2023

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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.281-282
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• 2023

The solid-state reference electrodes made of polyaniline-coated MnO₂ (SSRE-PAM) and their electrochemical characteristics were studied in simulated concrete pore solutions (SCPS) containing 0 and 3.5% NaCl. Saturated calomel electrodes (SCE) have been used to conduct electrochemical studies on the stability behavior of SSRE-PAM. Open circuit potential (OCP) and potentiodynamic polarization techniques were used to assess the corrosion performance of steel rebar exposed in SCPS with 0 and 3.5% NaCl using SSRE-PAM. The results demonstrate that the SSRE-PAM was capable of identifying steel rebar in a concrete environment that was either passive or active. Potentiodynamic polarization parameters such as E_corr and I_corr for steel rebar in SCPS containing 0 and 3.5%)NaCl are greater than that of the passive condition (0% NaCl). All the studies validate the importance of using SSRE-PAM for corrosion monitoring applications in concrete structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.73-79
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• 2016

Higher circuit breaker safety standards can be obtained by increasing the sustaining time of the latching section. This time increase is achieved through velocity reduction after contacting when the closing mechanism operates. The potential for the re-closing phenomenon to occur is also reduced by obtaining time to return open latch. In this study, the sustaining time for the latching section was increased through cam profile optimization based on the displacement response of the moving parts. In addition, the existing performance velocity was also satisfied. A multibody dynamics model of the circuit breaker was developed using ADAMS. To validate the model, simulation results were compared to experiment results. Then, cam profile optimization was carried out using an optimal design program PIAnO. Design variables selected included the radial direction of the cam. Design sensitivity analysis was carried out by design section as well. As a result of optimization, the sustaining time for the latching section was increased.

• Corrosion Science and Technology
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• v.17 no.2
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• pp.45-53
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• 2018

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 $PO{_4}^{3-}$ 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.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.147-154
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• 2017

This research was conducted to investigate the electrochemical properties of the thin air-formed oxide film-covered AZ31 Mg alloy. Native air-formed oxide films on AZ31 Mg alloy samples were prepared by knife-abrading method and the changes in the electrochemical properties of the air-formed oxide film were investigated in seven different electrolytes containing the following anions $Cl^-$, $F^-$, $SO{_4}^{2-}$, $NO_3{^-}$, $CH_3COO^-$, $CO{_3}^{2-}$, and $PO{_4}^{3-}$. It was observed from open circuit potential (OCP) transients that the potential initially decreased before gradually increasing again in the solutions containing only $CO{_3}^{2-}$ or $PO{_4}^{3-}$ ions, indicating the dissolution or transformation of the native air-formed oxide film into new more protective surface films. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) showed that there was growth of new surface films with immersion time on the air-formed oxide film-covered specimens in all the electrolyte. The least resistive surface films were formed in fluoride and sulphate baths whereas the most protective film was formed in phosphate bath. The potentiodynamic polarization curves illustrated that passive behaviour of AZ31 Mg alloy under anodic polarization appears only in $CO{_3}^{2-}$, or $PO{_4}^{3-}$ ions containing solutions and at more than $-0.4V_{Ag/AgCl}$ in $F^-$ ion containing solution.

• The korean journal of orthodontics
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• v.47 no.5
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• pp.306-312
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• 2017

Objective: The purpose of this study was to examine the effect of commercially available fluoride-containing oral rinses on the corrosion behavior of titanium alloys, which are the main components of orthodontic miniscrews. Methods: Four commercially available oral rinses (solution A, pH 4.46/260 ppm fluoride; solution B, pH 4.41/178 ppm fluoride; solution C, pH 6.30/117 ppm fluoride; and solution D, pH 4.17/3.92 ppm fluoride) were tested on titanium alloy (Ti-6Al-4V) circular plates, and saline was used as the control. The open-circuit potential and potentiodynamic polarization of these materials were measured. Thereafter, all samples were evaluated under a field-emission scanning electron microscope. Results: Among the tested oral rinses, except solution D, the more the fluoride content was, the greater was the corrosion potential downtrend; the corrosion resistance of the titanium alloy sample was also lowered significantly (p < 0.05). Field-emission scanning electron microscopic analysis of the surface morphology of the titanium alloy samples revealed that all samples had some defects, crevices, or pitting after exposure to the oral rinses than before treatment. In particular, the samples in solution A showed the most changes. Conclusions: Commercially available oral rinses having a high fluoride concentration and a low pH may reduce the corrosion resistance of titanium alloys used in dental appliances such as orthodontic titanium miniscrews and brackets.

• Restorative Dentistry and Endodontics
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• v.16 no.2
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• pp.18-32
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• 1991

The purpose of this study was to observe characteristic properties of amalgam through the polarization curves and SEM images from 4 type amalgams (Amalcap, Shofu spherical. Dispersalloy and Tytin) with 3 different surface finish procedures (polishing, burnishing and carving) by using the potentiostats (EG & GPARC) and SEM (Jeol JSM-35). After each amalgam alloy and Hg was triturated as the direction of the manufacturer by means of mechanical amalgamator (Samki), the triturated mass was inserted into the cylndrical metal mold which was 12 mm in diameter and 10 mm in height and was pressed with $100kg/cm^2$. 4 specimens of each type amalgam were burnished with egg burnisher and another 4 specimens of each type amalgam were carved with Hollenback carver. Above 8 specimens and remaining untreated 4 specimens were stored at room temperature for about 7 days. Untreated 4 specimens of each type amalgam were polished with abrasive papers (Deer) from #400 to #1200 and finally on the polishing cloth with $0.5{\mu}m$ and $0.06{\mu}m$ $Al_2O_3 $ powder suspended water. Anodic polarization measurements was employed to compare the corrosion behaviours of the amalgams in 0.9% saline solution at $37^{\circ}C$. The open circuit potential was determined after 30 minutes immersion of specimen in electrolyte. The scan rate was 1 mV/sec and the surface area of amalgam exposed to the solution was $0.64cm^2$ for each specimen. All the potentials reported are with respect to a saturated calomel electrode (SCE). SEM images of each specimen were taken after + 800 mV (SCE) polarization. The results were as follows: 1. The corrosion potential of high copper amalgam was more anodic than that of low copper amalgam. 2. The polished amalgam were more resistant to corrosion than any other burnished and carved amalgam. 3. In the case of polishing, current density of high copper amalgam was lower than that of low copper amalgam.

• Journal of Sensor Science and Technology
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• v.7 no.6
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• pp.426-431
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• 1998

This paper describes electrochemical etch-stop characteristics in THAH/IPA/pyrazine solution. I-V curves of n- and p-type Si in THAH/IPA/pyrazine solution were obtained. OCP(Open Circuit Potential) and PP (Passivation Potential) of p-type Si were -1.2 V and 0.1 V, and of n-type Si were -1.3 V and -0.2 V, respectively. Both n- and p-type Si, etching rates were abruptly decreased at potentials anodic to the PP. The etch-stop characteristics in THAH/IPA/pyrazine solution were observed. Since accurate etching stop occurs at pn junction, Si diaphragms having thickness of epi-layer were fabricated. Etching rate is highest at optimum etching condition, TMAH 25wt.%/IPA 17vol.%/pyrazine 0.1g/100ml. thus the elapsed time of etch-stop was reduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.681-686
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• 2017

Degradation is commonly observed in field-aged PV modules due to corrosion of the photovoltaic ribbon. The reduced performance is caused by a loss of fill factor due to the high series resistance in the PV ribbon. This study aimed to mitigate the degradation by corrosion using five sacrificial anodes - Al, Zn and their alloys - to identify the most effective material to mitigate the corrosion of the PV ribbon. The corrosion behavior of the five sacrificial anode materials were examined by open circuit potential measurements, potentiodynamic polarization tests, and galvanic current density and potential measurements using a zero resistance ammeter. Immersion tests for 120 hours were also conducted using materials and damp heat test tests were performed for 1500 hours using 4 cell mini modules. The Al-3Mg and Al-3Zn-1Mg sacrificial anodes had a low corrosion rate and reduced drop in power, making then suitable for long-term use.