Papers by Keyword: Corrosion

Paper TitlePage

Authors: Luca Giordano, Giuseppe Mancini, Francesco Tondolo
Abstract: Bond between steel and concrete in reinforced concrete structures plays a fundamental role. The stress transfer mechanism depends on the condition of the contact surface between the two materials, the mechanical characteristics of concrete near the rebar and on the available level of confinement. Corrosion of reinforcing bars in concrete structures modifies those three factors. Because of corrosion, on the rebar surface a granular oxide layer is present and with its expansion it generates a significant radial pressure; consequently tensile stresses grow till cracking of the concrete cover with a subsequent reduction of the confinement effect. Moreover the presence of a mechanical action modifies the resisting mechanism producing an increasing damage. In this study, a model is presented for the numerical simulation of experimental tests on r.c. ties subjected to mechanical action; furthermore some considerations on reinforced concrete ties subjected also to corrosion effect are reported. From those analyses it is possible to estimate a modified bond-slip law between the reinforcing bars and the concrete, in order to take into account the level of damage.
349
Authors: Orange Marshall
Abstract: A pre-action fire suppression system was installed in a portion of a US Army Reserve Component Headquarters building in the Southeastern United States, when the structure was constructed in 1995. A pre-action fire suppression system, which is normally kept at a standard internal air pressure using air compressors in the basement electrical-mechanical room, is designed to remain dry and only have water in it in the event of a fire. The installed pre-action system developed pinhole leaks due to what appeared to be galvanic corrosion. An in-situ epoxy lining technique was used to stop the corrosion and restore the integrity of the fire suppression system piping. The work included lining of all interior pre-action piping mains, risers, branch laterals and service piping to individual sprinkler head locations, installing new ½” sprinkler heads on the preaction system followed by recertification of the pre-action system. This presentation describes the in-place epoxy lining process and presents before and after photographs of the coated system used to eliminate the pin hole leak problem.
201
Authors: Sha Luo, Qing Qing Zhang, Yan Chang Zhang, Chao Li, Xiao Qing Xu, Tie Tao Zhou
Abstract: Magnesium alloys have a good application prospect in the fields of bone implants and cardiovascular stents due to their excellent properties, such as close density and elastic modulus to those of nature bone, high specific strength and rigidity, biodegradation and biocompatibility. In this paper, the feasibility of the use of the forged Mg-Li-X alloys (Mg-Li-Al-Zn-Ca-Sr) as biodegradable metals was investigated by immersion tests in the Hanks solution and skin-tissue implantation tests. The methods of SEM-EDS and XRD were used to research the corrosion morphology and corrosion products of the forged Mg-Li-X alloys after the in-vitro and in-vivo tests. At last, the in-vitro cytotoxicity was investigated by the MTT tests on L929 cells. Results showed that corrosion mechanism of the forged Mg-Li alloys was pitting and the surfaces were covered by Mg (OH)2,CaCO3 and Ca (H2PO4)2 . During the 5 weeks implantation period, the rats survived from the operation, which indicates that the elements and the compounds formed are non-toxic to the rats. The forged Mg-Li alloy showed Grade 0~1 cytotoxicity, which manifests the forged Mg-Li alloy has good biocompatibility and eligible toxicity for implant applications.
257
Authors: Diana Maria Vrânceanu, Mihai Tarcolea, Ana Iulia Gherghilescu, Florin Miculescu, Mihai Cosmin Cotrut
Abstract: Typical applications of metallic dental materials include metal-ceramic restorations, dental implants or orthodontic systems. Due to their contact with human tissues, corrosion resistance is one of the main requirements for dental materials. In the present paper, the corrosion behaviour in Fusayama Meyer artificial saliva solution (pH=5.2) on a selection of four different metallic dental materials (316 L steel, Au based alloy, cp-Ti, Ti6Al4V alloy) currently used in dentistry were investigated. The metallic dental materials have been investigated in terms of electrochemical analysis, chemical composition, morphology before and after corrosion, wettability and roughness. The results showed a hydrophilic behaviour in the case of Au based alloy, cp-Ti and Ti6Al4V alloy, and hydrophobic for 316L stainless steel. Considering the main electrochemical parameters, the cp-Ti alloy exhibited better corrosion resistance in artificial saliva with pH=5.2, followed by Au based alloy, Ti6Al4V alloy and 316L stainless steel. The main objective of the present paper was to evaluate the corrosion behaviour, as in important factor in the selection of metallic materials used in dentistry.
258
Authors: Chao Lu, Long Yu Xia, Ming Fang Zheng
Abstract: It is important for evaluating the condition of rock bolts to theoretically investigate the propagation of elastic waves in Rock bolt .In this paper, ultrasonic guided wave propagation and the interaction law with the artificial corrosion ring defect in the solid cylinder were studied through the rock bolt was modeled as a cylindrical. A large number of numerical simulation experiments were carried out using finite element method based on ABAQUS, The longitudinal mode of the propagation characteristics and law were analyzed in the solid cylinder, and the best excitation model and frequency were selected for the signal dispersion by combining curve with wave structures knowledge. The outcome of this research indicated that L(0,1) reflection coefficient is increased as well as during the depth incremental change when given a particular axial length; With the increment of the axial, L(0,1) and F(1,1) of the reflection coefficient maintain the similar trend when the ring defect depth coefficient 10%.
794
Authors: Yu Bai, Fang Li Yu, Jun Du, Wen Xian Wang, Ze Qin Cui, Zhi Hai Han, Jian Feng Yang
Abstract: Due to the low density and high specific strength, magnesium and its alloys have been extensively used in the automobile and aerospace applications, where the weight reduction is critical. However, they are highly prone to corrosion, which has greatly limited their application in the automotive and aerospace industries. This paper briefly reviews the technologies for improving the corrosion and wear resistance of magnesium alloys and finds that the widespread application of magnesium alloys is still limited by the lack of proper protective coatings. Therefore, there is still a need to explore new materials and methods for the effective protection of magnesium and its alloys.
307
Authors: N. Pistofidis, G. Vourlias, D. Chaliampalias, F. Stergioudis, Efstathios K. Polychroniadis
Abstract: In the present work the phases of the zinc coatings deposited with hot-dip galvanizing, pack cementation and wire flame spraying are examined with Scanning Electron Microscopy and Transmission Electron Microscopy. The different phases which are observed are identified with the combined results of electron and X-Ray diffraction. From the results it is concluded that pack cementation coatings are consisted by two different layers while hot dip galvanized coatings are composed by the same phases and additionally two extra phases of the Fe-Zn phase diagram. Flame sprayed coatings are composed by pure zinc, in the form of thin lamellae, together with nanocrystaline zinc oxide which is formed from the oxidation of liquid metallic droplets during the spray procedure.
93
Authors: Shubhra Mathur, Rishi Vyas, S.N. Dolia, Kanu Sachdev, S.K. Sharma
Abstract: Corrosion studies were carried out using potentiodynamic polarization method on amorphous, nanocrystalline and crystalline states of the alloy Ti60Ni40 in 0.5 M H2SO4 and 0.5 M HNO3 aqueous media at room temperature. The nanocrystalline state of Ti60Ni40 was obtained by removing about 10 μm from the air side surface (crystalline state) by polishing. The presence of nanocrystalline phase was confirmed by X-ray diffraction (XRD). It was found from polarization results that the corrosion current density was higher in the amorphous state than in the nanocrystalline state in both 0.5 M H2SO4 and 0.5 M HNO3 aqueous media. These results are corroborated by the weight loss studies which were carried out in both of these media. Results are discussed in the paper in the light of data reported in the literature on similar type of alloys.
179
Authors: Jian Hua Wu, Shao Hua Xing, Cheng Hao Liang, Yong Gui Yan
Abstract: The corrosion related electro-magnetic signature is easily detected by modern sensor deployed in mine and other signal measurement system, so the importance of reducing is rapidly growing today. The eliminating effect of shaft frequency signature by shaft insulating technique, passive grounding technique and active grounding technique was comparatively studied by physical scale model (PSM), and their influence on static electromagnetic signature was also studied by boundary element method (BEM). Simulation results suggested that active shaft grounding technique was the best way for eliminating shaft frequency signature, but static electromagnetic signature was stronger than that when the shaft was insulated from hull.
450
Authors: G. Vourlias, N. Pistofidis, D. Chaliampalias, F. Stergioudis
Abstract: One of the most effective methods for the protection of ferrous substrates from corrosion is zinc hot-dip galvanizing. Although this method has many advantages, it is characterized by a very negative effect on the environment. In the present work Zn coatings were formed with thermal spraying, pack cementation and fluidized bed reactor, which are friendlier to the environment. Their microstructure was characterized with X-ray diffraction and scanning electron microscopy, while their corrosion performance was estimated with exposure in a salt spray chamber. From this investigation it was deduced that CVD coatings are composed by two layers referring to Γ-Fe11Zn40 and δ-FeZn10 phase of the Fe-Zn phase diagram. By contrast the thermal coatings are very porous and composed by pure Zn. However, the corrosion performance of all coatings is similar. This conclusion is very important because it verifies that hot-dip galvanizing could be replaced by the other coating methods.
207
Showing 1 to 10 of 1457 Paper Titles