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This paper evaluates the effect of adding glycerol to the electrodeposition bath on the deposition efficiency and characteristics of Ni-Mo coating in concentrations ranging from 0.07 to 0.82 mol.L-1. Evaluation of the corrosion resistance was performed by means of weight loss tests in four different periods of immersion. Electrochemical techniques, such as obtaining polarization curves, linear polarization resistance, corrosion current density, corrosion potential, and electrochemical impedance spectroscopy were applied. Corrosion measurements were obtained in 0.5 mol.L-1 NaCl acid solution and 0.5 mol.L-1 NaOH alkaline solution. The morphology and microstructures of electrodeposited were analyzed using Scanning Electron Microscopy and Spectrometry X-Ray Diffraction. The effect of glycerol on Ni-Mo hardness was evaluated by Vickers microhardness measurements. The presence of glycerol in the electrodeposition bath increased the grain size and decreased the hardness of the coating. However, it promoted the formation of a more compact and less porous coating, increasing the corrosion resistance of the coating. Moreover, the addition of 0.82 mol.L-1 glycerol increases current efficiency, thereby reducing the amount of energy consumed during electroplating.

This work investigates the effect of the addition of glycerol on the microstructure, corrosion resistance, and efficiency of the electrodeposition process of Cu coating in an acid sulphate solution. The morphology and microstructures of electrodeposits were analyzed using Scanning Electron Microscopy (SEM), Spectrometry X-Ray Diffraction (XRD) and laser scanning confocal microscopy (LSCM). Evaluation of the corrosion resistance was performed in 2.0 mol⋅L−1 NaCl by means of weight loss tests and electrochemical techniques. The addition of glycerol resulted in a decrease in grain and crystallite sizes, a decrease in roughness and an increase in the tensile strain of the coating. The deposition efficiency and the corrosion resistance increased with the addition of glycerol exhibiting a maximum value at the concentration of 0.42 mol⋅L−1, increasing the efficiency of electrodeposition by approximately 96%. This is related to the roughness of the coating, which is minimal at this concentration.

Zinc electrodeposition is an economical process of Zn coating compared to conventional galvanic process. The galvanizing process is used in various industrial sectors to protect ferrous alloys during the corrosion process. In buildings, the galvanizing process is widely used to coat mortar protective screens. The electrodeposition of zinc has a relatively low cost compared to other coating materials for the same purpose; however, its corrosion resistance is lower than that of most protective deposits. This study evaluated the effect of adding glycerol to the electrodeposition bath on the corrosion resistance, deposition efficiency, morphology and microstructure of the zinc electrodeposit in concentrations ranging from 0.03 to 0.82 M. The electrodeposition was performed on carbon steel AISI 1020 with a current density of 10 mA.cm-2. The electroplating solution composition was 0.10 M ZnCl2, 2.80 M KCl and 0.32 M H3BO3. Electrodeposition time was 17.56 min, 5 µm thick coating, equivalent to the mass of 7.166E-3 g of zinc on the steel surface. Evaluation of the corrosion resistance was performed by means of the electrochemical tests of Anodic Voltammetry, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) as well as Weight Loss tests in NaCl 0.5 M in 4 (four) different period of immersion. The morphology and microstructures of electrodeposited were analyzed using the techniques of Scanning Electron Microscopy (SEM) and Spectrometry X-Ray Diffraction (XRD). The presence of glycerol in the electrodeposition bath decreased the deposition efficiency; however, it increased corrosion resistance and promoted the formation of more compact and refined electrodeposited coatings. Moreover, the results showed that the corrosion rate does not vary linearly with the addition of glycerol.

This paper shows the analysis performed on the corrosion parameters of three groups of reinforcing steel bars, two of these coated by electroplating process with Zinc (Zn) and Zinc-Nickel (Zn-Ni), and the other without any coating. It was used reinforced concrete specimens, which ones were grouped and then subjected to two different corrosion accelerating methods: aging wetting/drying cycles and salt spray exposure. Corrosion potential was measured to qualitative monitoring of the process and, after the end of the tests, corrosion rate was estimated by measuring the mass loss, to quantitative analyses. As it was expected, coated bars presented a better performance than the average bars regarding the corrosion resistance in chloride ions containing environments. It was also observed that the drying/ NaCl solution wetting cycles seems to be more severe than salt spray fog apparatus with respect to the acceleration of corrosion process. Resumo O presente trabalho avaliou os parâmetros de corrosão das barras de aço revestidas com Zinco (Zn) e com a liga Zinco-Níquel (Zn-Ni), por eletrodeposição, comparando-as com as tradicionalmente utilizadas, sem revestimento. Para isso, utilizaram-se amostras de concreto armado que foram submetidas a ensaios acelerados de corrosão por ação de cloretos (câmara de névoa salina – “salt spray” e ciclos de imersão e secagem). O potencial de corrosão das armaduras foi medido para monitoramento qualitativo do processo e, após o fim dos ensaios, estimaram-se as taxas de corrosão das barras, através da perda de massa, para análise quantitativa. As barras revestidas com Zn e Zn-Ni se mostraram mais resistentes à corrosão, quando comparadas com as barras convencionais, em ambientes com forte ação de cloretos e o envelhecimento por ciclos se mostrou muito mais eficiente na aceleração do processo de corrosão.

The present article focuses on the current status of research and development concerning corrosion resistance of Fe-Cr-based amorphous alloys and gives suggestions for further investigations aimed at improving the performance of these alloys and recommendations of possible new applications. These materials, which are usually obtained either as glassy bulk material or in coating and ribbon form, show high corrosion resistance and high wear resistance and are also relatively inexpensive compared to other amorphous metallic alloys. These characteristics can lead to promising applications of these alloys in which corrosion resistance and erosion-corrosion resistance are important. This review presents the results obtained in recent years, including the effect of amorphous structure, partial crystallization and composition on corrosion resistance, as well as applications of these alloys. Although advances have been made in studies concerning Fe-Cr-based amorphous alloys, there is an important limitation in terms of using them, which is the issue related to the high Mo content needed to achieve sufficient glass-forming ability and high corrosion resistance, which significantly increases the cost of these alloys. Therefore, the cost/benefit relation of these alloys needs to be improved by studying the effect of composition and structure on corrosion resistance and finding new applications of these alloys. Based on this literature review, possible applications and further investigations of these alloys are suggested.

Reinforced concrete is the main structural material used in the world in the construction of bridges, roads and commercial and residential buildings. One effective method for preventing corrosion of steel reinforcement is the application of galvanic coatings to the reinforcement itself. The present study evaluated the performance of three groups of reinforcing steel bars (black steel, used as a reference and rebars electroplated with Zinc and Zinc-Nickel alloys) to corrosion and adherence to the concrete matrix. For the analysis of corrosion, the specimens were subjected to two different accelerated corrosion tests: salt spray exposure and wet and dry semi-cycles. The corrosion potential was measured for the qualitative monitoring of the corrosion process and the corrosion rate was estimated. In order to evaluate the steel-concrete adherence, the pullout test was used, in accordance with RILEM-CEB-FIP. The results showed that Zinc and Zinc-Nickel coatings increased the durability of the reinforcing bars and the accelerated corrosion test of wetting and drying cycles proved to be more aggressive compared to the salt spray method to evaluate the corrosion process in the reinforced concrete specimens. Additionally, galvanized reinforcement reduced adherence to the concrete matrix.

Due to their maneuverability and operational flexibility, helicopters have become an important alternative means of transport in great metropolitan areas in Brazil in the last decade. Nonetheless, the number of helicopter accidents has increased in parallel. From 2006 to 2015, 211 accidents occurred and 1030 people died. The main aim of this article is to examine the causal factors that lead to the human error in the helicopter accidents which occurred in Brazil between 2006 and 2015 using HFACS. The most frequent HFACS categories were: decision error (68%), skill-based errors (59%), violations (33%), physical environment (15%), issues with inadequate supervision (46%), and organizational processes (15%). By identifying the higher level human errors leading to helicopter accidents, HFACS is useful a tool for accident investigations and accident prevention strategies. The current study provides practical suggestions for top managers for a better helicopter operational safety environment.

An investigation was made of the influence of long-term aging (up to 7000 h) at low temperatures (300 and 400 °C) on the corrosion and mechanical properties of a 2205 duplex stainless steel. The selective corrosion behavior of austenite and ferrite phases was found to reverse in response to aging treatment at 400 °C. The degree of Cr depletion (Ir/Ia) increased considerably with the increase in aging time at 400 °C and no self-healing process was observed even after aging for 7000 h. A good correlation was observed between the electrochemical results and the microhardness of ferrite phase.

The corrosion of concrete reinforcement is a worldwide problem with serious consequences to humans, including accidental deaths that may occur due to the degradation of this material. Thus, techniques that can measure concrete reinforcement corrosion and provide a reliable prediction of this phenomenon are fundamental for the technological development of these materials. The corrosion of steel bars embedded in concrete containing varying amounts of red mud (up to 30% of the total binder) was tested by electrochemical impedance spectroscopy (EIS), under partial immersion in a sodium chloride solution. The addition of red mud delayed the onset of corrosion and possibly also reduced the corrosion rate.

The present paper evaluates the corrosion resistance of four new amorphous Fe-Cr-based alloys containing Mo or Nb, as well as their thermal stability and the effect of their partial crystallization. Ribbons of Fe 68 B 20 Cr 12 , Fe 67.7 B 20 Cr 12 Mo 0,3 , Fe 67.7 B 20 Cr 12 Nb 0,3 and Fe 67.7 B 20 Cr 12 Nb 0,15 Mo 0,15 alloys were processed by the melt-spinning technique. The crystallization process of the four compositions occurs in a single-stage step with the simultaneous precipitation of fcc-Fe and Fe 3.5 B phases . The addition of Nb and/or Mo leads to an increase in the crystallization temperature, indicating that these elements stabilize the amorphous phase. The results also indicate that the alloy containing both Nb and Mo presented greater uniform corrosion resistance than the alloy containing either one or the other of these elements in NaCl and H 2 SO 4 solution.

Studies of the factors that enhance the corrosion resistance of electrodeposited Zn–Ni alloys are highly relevant due to these alloys' widespread industrial use as protective coatings for steel substrates. This paper reports on an investigation into the effect of the flow rate and the addition of gelatin to the plating bath on the corrosion resistance of Zn–Ni electrodeposits. An increase in the flow rate and gelatin content in the plating bath promoted an increase in the corrosion resistance of Zn–Ni deposit. This behavior cannot be explained in terms of composition because it involves the grain morphology of the electrodeposited alloy.

Zn–Ni alloys obtained by electrodeposition display a high protective capacity against corrosion and low hydrogen brittleness. The presence of Zn in Zn–Ni alloys provides cathodic protection of iron-based substrates while Ni increase the deposits corrosion resistance. A variety of additives are usually added to bath depositions to improve the efficiency of the deposition and the characteristics of the deposit. A Zn–Ni electrodeposited alloy was evaluated considering a duct-shape electrochemical cell with controlled electrolyte flow and the presence of gelatin as an additive was considered. The Ni content depends on gelatin concentration and if the flux is a laminar or turbulent one. Increased amount of gelatin and flow rate reduced the grain size of deposit.

The main reason for the study of Fe-based (FINEMET and NANOPERM) alloys was their magnetic properties. The nanocrystalline phases α-FeSi and α-Fe are responsible for the soft magnetic properties of FINEMET and NANOPERM alloys, respectively. A new type of amorphous and nanocrystalline FeCo-based alloy (HITPERM) has recently been produced. Its soft magnetic properties, which are attributed to the formation of α′-FeCo phase during the crystallization process, persist to the α–γ phase transformation at 980 °C. In spite of that the magnetic properties have got attention, the corrosion process on these amorphous and crystalline alloys became important due to the loss of magnetic properties. FINEMET alloys are more resistant to corrosion process than NANOPERM alloys in function of its Si content that acts on protector film formed during corrosion attack. The present work compares the magnetic flux density and the corrosion resistance in acid media of FINEMET, NANOPERM and HITPERM alloys, quantifies the losses on magnetic flux density due to corrosion process and introduces a new corrosion data about the amorphous and crystalline FeCoNbCuSiB alloy.

Made available in DSpace on 2018-11-26T15:27:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-01. Added 1 bitstream(s) on 2021-07-15T15:00:57Z : No. of bitstreams: 1 S1516-14392015000100098.pdf: 2442351 bytes, checksum: 145aaa62549d0ff382181954dd69f98d (MD5) Rotary-vacuum-filter mud (RVFM) is waste generated during the manufacturing process of titanium dioxide. In this work, RVFM and ceramic bricks containing different ratios of this waste are investigated. The mud samples were characterized using thermal analysis (TG/DTG). The aim of the present work was to determine the effect of adding RVFM on the ceramic properties of clay, such as apparent porosity, water absorption, linear shrinkage and flexural strength, used to produce red ceramics (bricks and roofing tiles). Samples were dried out at 110 degrees C and fired at 800 degrees C, 950 degrees C and 1100 degrees C. The addition of RVFM tends to increase the apparent porosity and water absorption and to decrease the flexural strength of the ceramic specimens. Based on the results, ceramic specimens with 20% RVFM content that are burned at 800 degrees C can not be used as bricks, and ceramic specimens with 20% RVFM content that are fired at 800 degrees C and 950 degrees C can not used as roofing tiles, according to Brazilian standards. Univ Fed Bahia, Dept Mat Sci & Technol, BR-40210630 Salvador, BA, Brazil MILLLENNIUM Inorgan Chem Brasil, Camacari, BA, Brazil ODEBRECHT Ambiental, BR-42810000 Camacari, BA, Brazil State Univ Sao Paulo, Dept Met & Mat Engn, BR-05508010 Sao Paulo, SP, Brazil State Univ Sao Paulo, Dept Met & Mat Engn, BR-05508010 Sao Paulo, SP, Brazil

The corrosion properties of a 22.5 wt. (%) Cr duplex stainless steel were investigated after long-term aging of 3000, 5000 and 7000 hours at 300 and 400 ºC. The corrosion resistance was measured based on mass loss in a FeCl3 10 wt. (%) solution and electrochemical measurements in a 0.1 M H2SO4 solution. The results indicate that the corrosion resistance decreased steadily up to 5000 hours of aging. However, the samples subjected to 7000 hours of aging showed better corrosion resistance than those aged for 3000 and 5000 hours. This effect is attributed to the phase transformation that occurs during aging, a finding which was confirmed by hardness, transmission electron microscopy and X-ray photoelectron spectroscopy measurements.

Trabalho completo: acesso restrito, p.75–82 Submitted by Bruna Lessa (lessbruna@gmail.com) on 2012-08-28T19:50:52Z No. of bitstreams: 1 (175).pdf: 714663 bytes, checksum: 75ec80019c24b29441bd7cf8fcca7725 (MD5) Made available in DSpace on 2012-08-28T19:50:52Z (GMT). No. of bitstreams: 1 (175).pdf: 714663 bytes, checksum: 75ec80019c24b29441bd7cf8fcca7725 (MD5) Previous issue date: 2005-01-03 The effects of bath composition and electroplating conditions on structure, morphology, and composition of amorphous Fe–Cr–P–Co deposits on AISI 1020 steel substrate, priorly plated with a thin Cu deposit, were investigated. The increase of charge density activates the inclusion of Cr in the deposit. However, above specific values of the charge density, which depend on the deposition current density, the Cr content in the deposit decreases. This Cr content decreasing is probably due to the significant hydrogen evolution with the increasing of deposition current and charge density. The effect of charge density on the content of Fe and Co is not clear. However, there is a tendency of increasing of Fe content and decreasing of Co content with the raising of current density. The Co is more easily deposited than the P, and its presence results in a more intense inhibition effect on the Cr deposition than the inhibition effect caused by P presence. Scanning electron microscope (SEM) analysis showed that Co increasing in the Fe–Cr–P–Co alloys analyzed does not promote the susceptibility to microcracks, which led to a good quality deposit. The passive film of the Fe–Cr–P–Co alloy shows a high ability formation and high protective capacity, and the results obtained by current density of corrosion, jcor, show that the deposit with addition of Co, Fe31Cr11P28Co30, presents a higher corrosion resistance than the deposit with addition of Ni, Fe54Cr21P20Ni5.