Papers by Keyword: Anodic Polarization Curve

Abstract: To clarify the effect of the acid solution type on corrosion resistance, the corrosion behavior of stainless steel brazed joints in HCl aqueous solution was evaluated through electrochemical measurements. Anodic polarization curves of a ferritic stainless-steel base metal, Ni-based brazing filler metals, and a brazed joint were recorded. In addition, in situ observations were conducted to observe the corrosion behavior of each structure of the brazed joint. Corrosion potentials of the brazing filler metal were lower than that of the base metal. In situ observations of the brazed joint revealed the order of corrosion in aqueous hydrochloric acid. According to the electrochemical measurements, under an actual corrosive environment, the brazing filler metal can function as an anode and selectively corrode. In addition, the anodic polarization curve of the brazed joint showed values between those of the polarization curves of the brazing filler metal and the base metal, indicating that the corrosion resistance could be electrochemically evaluated in HCl aqueous solution.

Abstract: The electropolishing behavior of high-purity aluminum in perchloric acid ethanol electrolytes is studied by the electrochemical methods. The morphologies of electropolished surface are examined by SEM. The results of anodic polarization shows that the limiting current density was decreased with the 1,2-propylene glycol and perchloric acid volume ratio increasing and the temperature decreasing. The results of SEM show that A salt film with porous pores on the electropolishing surface was formed on high-purity aluminum in the mixed solution of 1, 2 propylene glycol and perchloric acid at the volume ratio of 4:1 and 6:1, porosity of film increases from 12.3 % to18.4%, and the pore diameter of film increases from 19 nm to 23 nm with the current density increased from 120 mAcm^-2 to 140 mAcm^-2.

Abstract: The wear and corrosion of rare earth NiCrMoY alloy manufactured by atomization and oxygen-acetylene flame spray and high frequency induction remelting technique are investigated by a combination of scanning electron microscopy (SEM), energy spectrum, X-ray diffraction meter (XRD), uniform corrosion method of laboratory immersion test, anodic polarization curve of three electrodes potentiodynamic scan. The results indicate that Corrosion rate of NiCrMoY alloy coatings is better than that of Ni60A coatings in HCl, H₂SO₄, HNO₃ and artificial seawater, and its wear is much better than those of Ni60A coatings.

Abstract: The structures of reinforced concrete has been extensively increased with rapid development of industrial society. Furthermore, these reinforced concretes are often exposed to severely corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Thus, the corrosion problem of a steel bar embedded in the concrete is very important in terms of the safety and economic points of view. In this study, a multiple mortar test specimen (W/C:0.4) that had six types of cover thickness was prepared and immerged in flowing seawater for five years. And the effects of cover thickness and immersion years on the corrosion properties of the steel bars were investigated using electrochemical methods such as measuring corrosion potential, anodic polarization curve, and impedance. At the beginning of immersion (0 year), corrosion potentials exhibited increasingly nobler value with increasing the cover thickness. However, after being immersed for 5 years, the corrosion potentials conversely shifted in the positive direction with decreasing the cover thickness. As a result, the relationships between corrosion potential and cover thickness were not in good agreement with each other after 5 years. In addition, after 5 years, the thinner cover thickness, the higher value of impedance at 0.01Hz. It is considered that corrosive products deposited on the surface of the steel bar embedded in mortar specimen in the case of thinner cover thickness played the role as a resistance polarization which resulted in decreasing the corrosion current density. Consequently, it seemed to be somewhat problem that evaluation on the corrosion property in reinforced steel would be estimated by only the corrosion potential measurement. Therefore, it is suggested that we should take into account various parameters such as cover thickness, corrosion potential, and immersed years etc. for its accurate assessment. Keywords : Cover thickness, Corrosion potential, Anodic polarization curve, Impedance, Resistance polarization

Abstract: The anodic polarization curves of 21Cr-11Ni austenitic stainless steels with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods. The effect of RE on pitting corrosion resistance of 21Cr-11Ni stainless steels has been studied by the metallographic examination. The results show that sulfide and other irregular inclusions are modified to round or oval-shaped RE₂O₂S and RES after adding RE to 21Cr-11Ni stainless steesl. RE makes sulfide, and other irregular inclusions change to dispersed round or oval-shaped RE inclusions, effectively inhibits the occurrence of pitting corrosion, thereby enhancing the corrosion resistance of 21Cr-11Ni austenitic stainless steels.

Abstract: The anodic polarization curves of 2Cr13 stainless steel with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods. The effect of Ce on pitting corrosion resistance of 2Cr13 stainless steel has been studied by the metallographic examination. The results show that sulfide and other irregular inclusions are modified to round or oval-shaped Ce2O2S and CeS after adding Ce to 2Cr13 stainless steel.Ce makes sulfide, and other irregular inclusions change to dispersed round or oval-shaped Ce inclusions, effectively inhibits the occurrence of pitting corrosion, thereby enhancing the corrosion resistance of 2Cr13 stainless steel.

Abstract: The anodic polarization curves of 430 ferrite stainless steels with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods. The effect of RE on pitting corrosion resistance of 430 ferrite stainless steels has been studied by the metallographic examination. The results show that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES after adding RE to 430 ferrite stainless steesl. RE makes sulfide, and other irregular inclusions change to dispersed round or oval-shaped RE inclusions, effectively inhibits the occurrence of pitting corrosion, thereby enhancing the corrosion resistance of 430 ferrite stainless steels.

Abstract: The anodic polarization curves of 2205 duplex stainless steel with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods, The effect of rare earth on pitting corrosion resistance of 2205 duplex stainless steel has been studied by the metallographic examination. The results show that RE can effectively depress pitting corrosion, while the irregular inclusions of Al2O3, sulfide in the shape of clump are transformed into tiny dispersive round or oval RE inclusions, and it plays a good role in pitting resistance.