• Journal of the Korean Institute of Gas
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• v.9 no.4 s.29
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• pp.6-10
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• 2005

This paper was studied on the damage behavior of stainless steel (STS 304) for gas boiler with specific resistance. The electrochemical polarization test of STS304 for gas boiler was carried out. And the anodic polarization and damage aspect, such as pitting corrosion, was considered. With being low specific resistance, the passive current density of STS 304 increases, passive region and pitting potential is low. Also, the patting aspect of STS304 In specific resistance $74{\Omega}{\cdot}m$ water little appears, the pitting number increases and the damage behavior, such as pitting aspect, gradually grow bigger with being low specific resistance.

• Advances in Energy Research
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• v.2 no.2
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• pp.73-84
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• 2014

Fuel cells of proton exchange membrane type (PEMFC) working with hydrogen in the anode and ambient air in the cathode ('air breathing') have been prepared and characterized. The cells have been studied with variable thickness of the cathode catalyst layer ($L_{CL}$), maintaining constant the platinum and ionomer loads. Polarization curves and electrochemical active area measurements have been carried out. The polarization curves are analyzed in terms of a model for a flooded passive air breathing cathode. The analysis shows that $L_{CL}$ affects to electrochemical kinetics and mass transport processes inside the electrode, as reflected by two parameters of the polarization curves: the Tafel slope and the internal resistance. The observed decrease in Tafel slope with decreasing $L_{CL}$ shows improvements in the oxygen reduction kinetics which we attribute to changes in the catalyst layer structure. A decrease in the internal resistance with $L_{CL}$ is attributed to lower protonic resistance of thinner catalyst layers, although the observed decrease is lower than expected probably because the electronic conduction starts to be hindered by more hydrophilic character and thicker ionomer film.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.227-232
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• 2000

The LSM-YSZ composite electrode as a mixture of LSM and YSZ shows percolation characteristics. It was identified that the polarization resistance of LSM-YSZ composite electrode depend on YSZ connectivity by changing powder size ratio of the DLSM/DYSZ. That is, YSZ in composite electrode showed low electrochemical activity without YSZ connectivity. However, the polarization resistance decreased abruptly with YSZ connectivity due to high electrochemical activity of YSZ in composite electrode. Because the amount of three phase boundary is dependent on LSM and YSZ particle size, the polarization resistance of cathode decreases as LSM and YSZ particle size decreases.

• Journal of Industrial Technology
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• v.18
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• pp.259-265
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• 1998

The molecular weights of surfactant SDS(M.W. 288) and SLS(M.W. 420) are smaller than the molecular weigh cut-off of cellulose acetate membrane used in this study. However, 20% of SDS and 67% of SLS were rejected by cellulose aectate membrane. The higher rejection rate of SLS than that of SDS is due to the longer hydrophobic chain and greater molecular weight. There was no resistance to permeation rate by membrane fouling. Most of permeation resistance was due to the concentration polarization. Permeation rate was declined with operating time and with increase in concentration of surfactant due to concentration polarization.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.698-703
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• 1998

The pervaporation experiments of aqueous solutions of trichloroethylene (TCE) and chlorobenzene (CB) through the silicone rubber (polydimethylsiloxane, PDMS) membrane were carried out and the effect of concentration polarization on the separation characteristics was investigated. The resistance-in-series model was used to explain the boundary layer resistance. It was clear that the concentration polarization phenomenon had a significant effect on the permeation behavior in the pervaporation separation of the trace organic chlorides from aqueous solutions. With the same membrane thickness, the permeation of TCE, which has a stronger affinity for the PDMS, appeared to be more influenced by the boundary layer resistance than that of CB. The effect of boundary layer resistance was reduced and the membrane resistance became dominant with increasing membrane thickness at a given hydrodynamic condition. The separation factor was increased to approach the intrinsic separation factor of the membrane with its thickness.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.35-40
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• 2004

In order to understand alloying effects on the corrosion resistance of Ti-(10$\sim$20)%Zr-(2$\sim$8%)Nb-0.2%Pd alloys, Polarization curves were measured at 5%HCI solution. The results were interpreted in terms of two parameters obtained by the molecular orbital calculation ; one is the bond order($B_{\circ}$) and the other is the metal d-orbital level($M_{d}$). $B_{\circ}$ is a measure of the strength of covalent bonds between titanium and alloying elements. $M_{d}$ is correlative with the electronegativity of elements. It was found that increasing of Zr and Nb with higher $B_{\circ}$ values showed a lower critical anodic current density in the polarization curve and hence higher corrosion resistance. On the other hand, increasing of Zr and Nb with higher $M_{d}$ values showed a higher corrosion resistance.

• Korean Journal of Metals and Materials
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• v.47 no.10
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• pp.635-643
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• 2009

The resistance to pitting corrosion of Fe-Cr alloys was evaluated by performing potentiodynamic polarization and critical pitting temperature (CPT) tests. For the potentiodynamic polarization tests, various standards were applied, i.e., KS D 0238 (wet, dry), ASTM G 61, and ISO 17475, showing different potentiodynamic polarization results including pitting potentials. ASTM G 61 and ISO 17475 standards presented relatively higher pitting potential while KS D 0238 (dry) indicated lower values than the others. Effects of surface roughness, scan rates, and exposure time to air before tests were also investigated. CPT tests were performed under two different applied potentials, 300 m$V_{SCE}$ and 200 m$V_{SCE}$ in deaerated 1 M NaCl aqueous solution. CPT values and the polarization test results showed a linear relationship.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.125-131
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• 2002

This paper was studied on the effect of temperature on corrosion of absorption refrigeration systems using $LiBr-H_2O$ working fluids. In the fresh water and 62 % lithium bromide solution at $70^{\circ}C$, polarization test of SS 400, Cu(C1220T-OL) and Al-Ni bronze was carried out. And polarization behavior, polarization resistance characteristics, corrosion rate(mmpy) and corrosion sensitivity of materials forming absorption refrigeration systems was considered. The main results are as following: (1) As the experimental temperature increase, the change of corrosion rate of Al-Ni bronze become duller than SS 400 and Cu in 62% lithium bromide solution. (2) According as corrosion environment is changed from fresh water to 62% lithium bromide solution, potential change of Cu and Al-Ni bronze become less noble than SS 400. (3) The corrosion sensitivity of Al-Ni bronze was duller than that of Cu and SS 400 in 62% LiBr solution.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.71-76
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• 2021

Ag925, silver with added copper, is popular alloy due to its low price. However, it has a difficult to use because of the low corrosion resistance. In various alloys, neodymium (Nd) works as an element to improve corrosion resistance by reacting with interstitial elements in the alloy. When 1.5 wt. % Neodymium was added to Ag925, the potential on the activated polarization in a potentiodynamic polarization test was increased from -0.15 V to -0.05 V. Ag925 with added neodymium showed the passivation after activation polarization. But When the potential increased around 50 mV, the current density is increased to 3 × 10-3. Ag925 with the 1.5 wt. % Nd had the low corrosion rate.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.156-162
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• 2020

The objective of this study was to investigate delayed oxygen evolution and localized corrosion resistance of titanium alloys by performing potentiodynamic polarization, potentiostatic polarization, and Mott-Schottky measurements. Delayed oxygen evolution was compared among titanium alloys, 316 stainless steel, and platinum. Difference in delayed oxygen evolution between titanium alloys and other metals was attributed to specific surface characteristic of each metal. Delayed oxygen evolution of titanium alloys resulted from the predominant process of ionic conduction over electronic conduction. The effect of oxygen evolution on localized corrosion of titanium alloys was investigated using electrochemical critical localized corrosion temperature (E-CLCT) technique. Mott-Schottky measurement was performed to clarify the difference in film properties between titanium alloys and stainless steels. Titanium alloys were found to have much lower donor density than stainless steels by 1/28. These results indicate that delayed oxygen evolution has little influence on the concreteness of passive film and the resistance to localized corrosion of titanium alloys.