Papers by Keyword: Corrosion Resistance

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Authors: Hai He Luo, Qi Zhou Cai
Abstract: A ZrO2-Y2O3-containing composite ceramic coating was firstly in situ prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in an alkaline silicate-containing electrolyte. The morphology, chemical composition and corrosion resistance of the PEO coating were investigated by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectrometer, dropping corrosion and electrochemical corrosion test. The results showed that the ceramic coating consisted of two distinct structural layers: an outer loose layer and an inner dense layer; it was composed of t-ZrO2, Y2O3, SiO2 and some magnesium compounds, such as MgO, MgF2 and Mg2SiO4. In addition, the ceramic coating also showed excellent dropping and electrochemical corrosion resistance, which was mainly attributed to its special phase composition and microstructure.
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Authors: Zheng Han Chen, Xiao Feng Sun, Yuan Lin Huang
Abstract: Nickel aluminum bronze is widely used in manufacturing propeller, in marine environment, propellers are easy to generate corrosion, it is important to find efficient solutions to repair corrosive propeller. In this study, it utilized OM and SEM to observe the failure modes of propeller, and discuss the feasibility of using cold spray (CS) technology to repair corrosive propeller. The study showed that failure modes of propeller includes corrosion, cavitations and abrasion, cold spray is possible an effective solution to solve these failures.
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Authors: Norbert Kazamer, Dragos Toader Pascal, Gabriela Marginean, Viorel Aurel Şerban, Cosmin Codrean, Ion Dragoş Uţu
Abstract: In order to be competitive, it is demanded to have thin, tough and long lasting coatings. An important aspect is to use stable deposition technologies. As Cr assures wear, corrosion and high temperature resistance, the most employed coatings in industry generally contain Cr. Nevertheless, Cr is a hazardous element for the humans’ health, therefore, sustainable alternatives are needed to be implemented. The aim of this work is to investigate the microstructure, hardness, corrosion resistance and wear behavior of the novel WC-CoMo compared to conventional WC-Co coatings. So far, WC-CoMo coatings are not part of state of the art regarding the Atmospheric Plasma Sprayed (APS) coatings. WC-Co powder in plain form and mechanically mixed with Mo was deposited using the APS method on standardized Type A Almen Strips (C67 steel). The size of the powder grains varies between 5 µm and 30 µm. The obtained samples were investigated by means of Scanning Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, X-Ray Diffraction, and hardness, wear and corrosion behavior were also evaluated. Results revealed formation of different intermetallic phases around the WC particles, which have a benefic influence on the coating characteristics and microstructure.
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Authors: Anna da Forno, Massimiliano Bestetti
Abstract: In this paper a protection process against corrosion and wear for AM60B magnesium alloys, by multilayer approach, is related. The coating consists of a porous oxide layer, obtained in micro-arc anodizing regime, and two or three layers deposited by sol-gel technique. The anodic oxidation pre-treatment improves the adhesion of the sol-gel layers, which are responsible for the sealing of the anodic oxide pores and for the corrosion protection effect. In addition the multilayer system significantly improves AM60B alloy wear resistance. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) were employed to assess morphology and crystallographic structure. Electrochemical polarization and wear tests were performed in order to evaluate the corrosion resistance behaviour and the wear resistance of the coated magnesium alloys.
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Authors: Dong Sheng Xia, Yu Zhou Gao, Hui Chen Zhang, Yan Yu
Abstract: The work aims to investigate the anti-corrosion behavior of silane treated LY12 aluminum alloy (AA LY12) and optimize the process conditions of silane treatment. The silane films were prepared on AA LY12 from γ-aminopropyltriethoxysilane (γ-APS) hydrolized in ethanol/water mixture by dip coating method. The optimum process parameters were obtained from the orthogonal designs in terms of silane solution concentration, ethanol/water ratio, dipping time, curing temperature and curing time. Prior and after silane treatment, the surface of AA LY12 was characterized by contact angle measurements and scan electron microscopy (SEM). The potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements (EIS) were employed to study the anti-corrosion characteristics of silane films on AA LY12. The impedance plots were fitted with the different equivalent circuits. Furthermore, the influence of the above process parameters of silane treatment on film formation and anti-corrosion performance was explored. The results indicate that the γ-APS treated AA LY12 significantly improved the corrosion resistance, compared to the untreated one.
1891
Authors: J. Jin, Y.B. Chen, K.W. Gao, X.l. Huang
Abstract: The corrosion resistance of metal-N double-element alternate implanted M50NiL bearing steel was investigated by potentiodynamic polarization and detection methods of SEM, XPS, AES and TEM. The results showed that ion implanted M50NiL can increase the corrosion potential of substrate, reduce the corrosion active points and inhibit the corrosion reaction induced at the grain boundaries. The formed amorphous layer and strengthening phases take main roles in improving the corrosion resistance of M50NiL bearing steel.
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Authors: Lian Xi Chen, Xiao Jian Wang, Wei Li
Abstract: A biodegradable Mg-4Zn-0.6Zr alloy with different content of strontium (Sr) was prepared and studied for orthopedic applications biomaterials. The effects of Sr on the microstructure and corrosion degradation of the as-cast Mg-4Zn-0.6Zr-xSr (ZK40xSr) alloys were investigated. The optical micrograph (OM) observation, energy-dispersive spectrometer (EDS), X-ray diffractometer (XRD) and immersion test were used. The grain size of Mg-4Zn-0.6Zr alloys was reduced obviously with the addition of Sr. The excess of Sr would lead to grain size increasing and grain boundaries widening. The possible presence of the following constituent phases in the grain boundaries: α-Mg, Mg17Sr2, MgZn, ZnxSry binary and MgxZnySrz ternary phase. The formation of ZnxSry and MgxZnySrz phase owed to the larger difference of electronegativity values of Zn and Sr. The immersion tests indicated that the average corrosion rate of the as-cast ZK40xSr alloys increased with the increase of Sr content. It contributed to the micro-galvanic corrosion between the α-Mg with the continuous distribution of grain boundaries precipitates.
71
Authors: Ai Ju Li, Hong Yu Chen, Long Chuan Dou, Hui Wang, Wei Zhang
Abstract: The effects of different Sn or Se content on the corrosion behavior of lead-Sn or Pb-Sn_Se alloy in sulfuric acid solutions were investigated by metallurgical microscope, SEM, and weight loss tests. It was found that the addition Sn acts as grain coarser, but Se acts as grain refiner and Pb-Sn-Se alloys feature smaller grains. SEM for the corrosion layer indicated that the intergranular corrosion occurs on the surface of alloys with high Sn content (>1.wt%), but the general corrosion occurs on the surface of Pb-Sn alloys with low Sn content (<1.wt%) and all Pb-Sn-Se alloys. And The structure of corrosion layer and the eroded degree are relative to the height of the strap alloys above the plate. And the 1cm strap alloy above the plate was cathodically protected and almost no corrosion problems appeared. The corrosion rate of alloys containing Se is lower than Pb-Sn binary alloys. And the higher of Se content, the lower of corrosion rate. The results demonstrated that Pb-Sn-Se alloys show the potential for application as the negative strap in VRLA batteries.
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Authors: Bei Bei Xie, Wen Li Han, Yan Jun Zhang, Zhong Ping Xu, Yao Hui Yang, Yi Gang Zhang
Abstract: In order to ravel out the problem of serious corrosion and difficult repeated construction on the sea, the fluorocarbon coatings for external surface of ocean platform has been researched. The UV light stability, salt fog resistance, acid and alkali corrosion resistance of fluorocarbon coatings are investigated. The comparison data between fluorocarbon coating and chlorinated rubber coatings, acrylic polyurethane coatings and silicone coatings are given.
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