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Xiao K.,University of Science and Technology Beijing | Dong C.,University of Science and Technology Beijing | Li X.,University of Science and Technology Beijing | Wei D.,Society Service Center
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2011

The galvanic corrosion of an AZ91D magnesium alloy coupled with 316L stainless steel using accelerated testing in salt spray fog has been investigated by using the scanning Kelvin probe (SKP) technique. The results show that the galvanic effects for AZ91D magnesium alloys are affected by the potential difference between anode and cathode by analyzing corrosion products and SKP Volta potential maps. The galvanic effect of AZ91D magnesium alloy coupled with 316L stainless steel is very significant during accelerated testing in the initial stage of salt spray fog because the potential difference between AZ91D magnesium alloy and 316L stainless steel is about -1.28 V. The galvanic corrosion occurs mainly in the interface near AZ91D magnesium alloy, and 316L stainless steel has no obvious corrosion. With the salt spray test time increasing, the corrosion of the AZ91D magnesium alloy is accelerated and the coverage area of corrosion products expanded. The Volta potential difference of galvanic sample increases from -1.29 V to -1.53 V after 24 h salt spray test. The galvanic corrosion effect of AZ91D magnesium alloy is increased. The corrosion products of AZ91D magnesium alloy have a protective effect. The galvanic corrosion effect is reduced when the corrosion product increases to cover the surface of the specimen. Copyright © 2011, Northwest Institute for Nonferrous Metal Research. Source


Xiao K.,University of Science and Technology Beijing | Dong C.,University of Science and Technology Beijing | Wei D.,Society Service Center | Wu J.,University of Science and Technology Beijing | And 2 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2016

Galvanic corrosion on samples of AZ91D magnesium alloy coupled with 2A12 aluminum alloy during neutral salt spray test was investigated. The variations of the surface potential were measured using scanning kelvin probe (SKP). The results showed that galvanic effect on the corrosion of AZ91D magnesium alloy is closely related to the potential difference between the anodic and cathodic materials. In the initial period, corrosion only occurred in a narrow area at the coupling interface because of the limited distance galvanic current. Then, the corrosion rate of 2A12 aluminum alloy was accelerated due to its poor stability in strong alkali environment, which was attributed to the strong alkalization caused by the corrosion of AZ91D magnesium alloy. With the increase of the potential of 2A12 aluminum alloy as a result of the continuous covering of corrosion products, the potential difference between the two materials was enlarged, which enhanced the galvanic corrosion. © 2016, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg. Source


Liu A.-q.,University of Science and Technology Beijing | Xiao K.-k.,University of Science and Technology Beijing | Dong C.-f.,University of Science and Technology Beijing | Wang E.-q.,Xinxing Ductile Iron Pipes Co. | And 3 more authors.
Corrosion and Protection | Year: 2012

Pure Zn, Zn-Al alloy and Zn-Al pseudo-alloy coatings were prepared on Q235 steel surface by arc spraying technique. The corrosion resistance of these coatings was investigated by immersion testing and electrochemical measurements in 3.5 % NaCl solution. The surface morphology of the samples after test and the phase composition of corrosion products were analyzed by using electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the corrosion resistance of the coatings decreased sequentially in the order of Zn-Al pseudo alloy coating, Zn-Al alloy coating, and pure Zn coating. Source


Xiao K.,University of Science and Technology Beijing | Zhang X.,University of Science and Technology Beijing | Dong C.,University of Science and Technology Beijing | Wei D.,Society Service Center | And 2 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2012

The corrosion behaviors of Fe-Cr alloy under three different pH values solutions with Cl - and SO 4 2- were investigated by localized electrochemical impedance spectroscopy (LEIS) measurements and the corrosion products were analyzed by laser Raman spectrometry. The results show that the high corrosion resistance of Fe-Cr Alloy is attributed to a passive film which is formed more easily when the alloy contains a large quantity of Cr element. However, its corrosion resistance varies in the solutions with different pH values, especially in the initial corrosion. The average impedance values in neutral and alkaline solution are much higher than that in acidic solution because the passive film is more likely to dissolve in the acidic condition. Moreover, the destructive effect of Cl - and SO 4 2- ions on the passive film is also demonstrated in corrosion process through the change of the impedance value with the steeping time. ©Wuhan University of Technology and SpringerVerlag Berlin Heidelberg 2012. Source


Xiao K.,University of Science and Technology Beijing | Dong C.-F.,University of Science and Technology Beijing | Wei D.,Society Service Center | Wu J.-S.,University of Science and Technology Beijing | And 2 more authors.
Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing | Year: 2011

Scanning Kelvin probe (SKP) was used for measuring the corrosion behavior of carbon steel with a defected epoxy coating after neutral salt spray test, and the volta potential changes of carbon steel at different stages of neutral salt spray test were analyzed. It is shown that the defect formed by the damaged epoxy/carbon coating provides a way for the corrosive medium to contact the carbon steel matrix. The potential of carbon steel is more negative at the defect point than that under the coating, resulting in anodic dissolution at the defect point. After some time of neutral salt spray test, insoluble corrosion products can cover the bare defect, leading to the potential at this part shifting to more positive values. Consequently, the defect becomes a cathode, while its vicinity under the coating exists as an anode. Meanwhile, the potential difference between the new cathode and the new anode offers a driving force for continuous corrosion under the coating. Therefore, with the corrosion developing, there would be a considerable corrosive medium and corrosion products aggregating at the interface, which destroy the binding between the epoxy coating and carbon steel, leading to the appearances of bubbling and peeling. Source

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