• Journal of the Korean Chemical Society
• /
• v.57 no.2
• /
• pp.272-278
• /
• 2013

Extract of ginger has been evaluated as a green inhibitor for the corrosion of steel in sulfide polluted NaCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Potentiodynamic polarization measurements showed that this extract acts as a mixed type inhibitor but mainly inhibits the cathodic reaction. The inhibition efficiency was found to increase with inhibitor concentration reaching to approximately 83.9% using 250 ppm of ginger. Nyquist plots show a single capacitive loop in uninhibited and inhibited solutions. From EFM the causality factors are very close to theoretical values which indicate that the measured data are of good quality. The adsorption process of the studied extract on steel surface obeys Temkin adsorption isotherm. The results obtained from the different electrochemical techniques were in good agreement which prove the validity of these tools in measurement of corrosion rate. Ginger extract has no effect on Escherichia Coli and can be applied safely on waste water treatment plants.

• Corrosion Science and Technology
• /
• v.21 no.2
• /
• pp.147-157
• /
• 2022

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.

• Corrosion Science and Technology
• /
• v.16 no.3
• /
• pp.100-108
• /
• 2017

In this investigation corrosion behavior of newly developed high-pressure die cast Al-Ni (N15) and Al-Ni-Ca (NX1503) alloys was studied in 3.5% NaCl solution. The electrochemical corrosion behavior was evaluated using open circuit potential (OCP) measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization results validated that NX1503 alloy exhibited lower corrosion current density ($i_{corr}$) value ($5.969{\mu}A/cm^2$) compared to N15 ($7.387{\mu}A/cm^2$). EIS-Bode plots revealed a higher impedance (${\mid}Z{\mid}$) value and maximum phase angle value for NX1503 than N15 alloy. Equivalent circuit curve fitting analysis revealed that surface layer ($R_1$) and charge transfer resistance ($R_{ct}$) values of NX1503 alloy was higher compared to N15 alloy. Immersion corrosion studies were also conducted for alloys using fishing line specimen arrangement to simultaneously measure corrosion rates from weight loss ($P_W$) and hydrogen volume ($P_H$) after 72 hours and NX1503 alloy had lower corrosion rate compared to N15 alloy. The addition of Ca to N15 alloy significantly reduced the Al3Ni intermetallic phase and further grain refinement may be attributed for reduction in the corrosion rate.

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

• Journal of Welding and Joining
• /
• v.15 no.5
• /
• pp.124-133
• /
• 1997

Corrosion behavior of welded SWS400 steel used for bridges was studied in a range of the acid-rain environment using immersion, potentiodynamic polartization, polarization resistance, and galvanic corrosion tests. The SWS400 steel exhibited active corrosion behavior in the range of acid-rain environment, i.e. no passivation. As the results of immersion corrosion test, Tafel extrapolation method, and polarization resistance measurement, the average corrosion rats of the steels were 0.31-0.72 mm/year in the pH of 4-5, and 0.17 mm/yera in the pH 6, respectively. The steel showed a resistance to corrosion in the pH 6. The observed active behavior of SWS400 steel in chloride-containing environment indicated that the chloride ions exerts a detrimental influence on the formation of passive films. Galvanic corrosion was observed between the weld and the base metals because the weld is anodic to the base metal.

• The Journal of Korean Academy of Prosthodontics
• /
• v.31 no.3
• /
• pp.423-446
• /
• 1993

Titanium and its alloys are finding increasing use in medical devices and dental implants. The strong selling point of titanium is its resistance to the highly corrosive body fluids in which an implant must survive. This corrosion resistance is due to a tenacious passive oxide or film which exists on the metal's surface and renders it passive. Potentiodynamic polarization measurement is one of the most commonly used electro-chemical methods that have been applied to measure corrosion rates. And the potentiodynamic polarization test supplies detailed information such as open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. This study was designed to compare the corrosion resistance of the commonly used dental implant materials such as CP Ti, Ti-6A1-4V, Co-Cr-Mo alloy, and 316L stainless steel. And the effects of galvanic couples between titanium and the dental alloys were assessed for their useful-ness-as. materials for superstructure. The working electrode is the specimen , the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is made of carbon. In $N_2-saturated$ 0.9% NaCl solutions, the potential scanning was performed starting from -800mV (SCE) and the scan rate was 1 mV/sec. At least three different polarization measurements were carried out for each material on separate specimen. The galvanic corrosion measurements were conducted in the zero-shunt ammeter with an implant supraconstruction surface ratio of 1:1. The contact current density was recorded over a 24-hour period. The results were as follows : 1. In potential-time curve, all specimens became increasingly more noble after immersion in the test solution and reached between -70mV and 50mV (SCE) respectively after 12 hours. 2. The Ti and Ti alloy in the saline solution were most resistant to corrosion. They showed the typical passive behavior which was exhibited over the entire experimental range. Therefore no breakdown potentials were observed. 3. Comparing the rupture potentials, Ti and Ti alloy had the high(:st value (because their break-down potentials were not observed in this study potential range ) followed by Co-Cr-Mo alloy and stainless steel (316L). So , the corrosion resistance of titanium was cecellent, Co-Cr-Mo alloy slightly inferior and stainless steel (316L) much less. 4. The contact current density sinks faster than any other galvanic couple in the case of Ti/gold alloy. 5. Ag-Pd alloy coupled with Ti yielded high current density in the early stage. Furthermore, Ti became anodic. 6. Ti/Ni-Cr alloy showed a relatively high galvanic current and a tendency to increase.

• Corrosion Science and Technology
• /
• v.6 no.6
• /
• pp.311-315
• /
• 2007

The anodic polarization behavior of equiatomic TiNi shape memory alloy with pure titanium as a reference material was investigated by means of open circuit potential measurement and potentiodynamic polarization technique. And the structure of passive films on TiNi intermetallic compounds was also conducted using AES and ESCA. While the dissolved Ni(II) ion did not affect the dissolution rate and passivation of TiNi alloy, the dissolved Ti(III) ion was oxidated to Ti(IV) ion on passivated TiNi surface at passivation potential. It has also been found that the Ti(IV) ion increases the steady state potential, and passivates TiNi alloy at a limited concentration of Ti(IV) ion. The analysis by AES showed that passive film of TiNi alloy was composed of titanium oxide and nickel oxide, and the content of titanium was three times higher than that of nickel in outer side of passive film. According to the ESCA analysis, the passive film was composed of $TiO_2$ and NiO. It seems reasonable to suppose that NiO could act as unstabilizer to the oxide film and could be dissolved preferentially. Therefore, nickel oxide contained in the passive film may promote the dissolution of the film, and it could be explained the reason of higher pitting susceptibility of TiNi alloy than pure Ti.

• Journal of the Korean Society for Heat Treatment
• /
• v.9 no.2
• /
• pp.103-111
• /
• 1996

In this paper, we studied on both electrochemical polarization behaviors and pitting characteristics of ultra high strength Al-Cu-Li-Mg-Ag-Zr alloys(named C1 and C2) and 2090 alloy according to their treatments in the deaerated 3.5% NaCl, using by the potentiodynamic and the potentiostatic method, SEM micrograph and surface roughness including depth of pitting attack. With the cyclic polarization curves, the hysteresis of the C1 and C2 alloys appeared more remarkably than that of the 2090 alloy, because of precipitation microstructural difference between C1, C2 alloys and 2090 alloy. In the pitting experiments, the correlations between pitting growth and aging conditions were analyzed with the SEM micrograph and measurement of the pit depth.

• Journal of Electrochemical Science and Technology
• /
• v.11 no.3
• /
• pp.257-272
• /
• 2020

This study covers the stages of testing whether the azo dye with chemical name (E)-5-[(4-(benzyl(methyl)amino)phenyl)diazenyl]-1,4-dimethyl-1H-1,2,4-triazol-4-ium zinc (II) chloride (DMT), known as Maxilon Red GRL in the dye industry, can be used as an anticorrosive feasible inhibitory agent, especially in industrial areas other than carpet, yarn and fibre dyeing. These test stages consist of the electrochemical measurement techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) for diverse concentrations and durations. The adsorption of the viewed DMT molecule on the mild steel surface obeyed the Langmuir isotherm. The zero charge potential (PZC) of mild steel was also found to assess the inhibition mechanism in containing DMT solution. The inhibition performance of DMT on the mild steel in a 1.0 M HCl solution was also investigated using methods such as metal microscope, atomic force microscope (AFM) and field emission scanning electron microscope (FE-SEM).

• Corrosion Science and Technology
• /
• v.3 no.3
• /
• pp.118-126
• /
• 2004

The correlation between sensor output and corrosion rate of reinforcing steel was evaluated by laboratory electrochemical tests in saturated $Ca(OH)_2$ with 3.5 wt.% NaCl and confirmed in concrete environment. In this paper, two types of electrochemical probes were developed: galvanic cells containing of steel/copper and steel/stainless steel couples. Potentiodynamic test, weight loss measurement, monitoring of open-circuit potential, linear polarization resistance (LPR) measurement and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of steel bar embedded in concrete. Also, galvanic current measurements were conducted to obtain the charge of sensor embedded in concrete. In this study, steel/copper and steel/stainless steel sensors showed a good correlation in simulated concrete solution between sensor output and corrosion rate of steel bar. However, there was no linear relationship between steel/stainless steel sensor output and corrosion rate of steel bar in concrete environment due to the low galvanic current output. Thus, steel/copper sensor is a reliable corrosion monitoring sensor system which can detect corrosion rate of reinforcing steel in concrete structures.