Corrosion Resistance Of Metals Research Articles

Integration of novel hybrid composite discharge electrode with semi-pilot novel cross-flow electrostatic precipitator

ABSTRACTWet electrostatic precipitators (WESPs) are modern-era pollution control systems specifically designed to capture ultrafine particles as well as acid mist, highly resistive and sticky particles; however, this requires the use of expensive corrosion-resistant metal alloys. The work presented here is part of a continuing study at Ohio University aimed at reducing the cost of WESPs by using a novel combination of a polymer collector surfaces with a hybrid composite discharge electrode. In this study, a hybrid composite discharge electrode was tested, for the first time, inside a semi-pilot-scale experimental setup, with collection surfaces consists of a vertical array of strands. Particle laden gases were passed through this array of polymer ropes, which were kept wet by a small flow of water. The discharge electrodes were composite laminates of carbon fibers in a polymer matrix enclosing a metal mesh. The preliminary results showed that this new integrated system of composite discharge electrode and polymer collector surfaces can match or exceed the performance of a conventional metal alloy electrostatic precipitator (ESP) with metal discharge electrodes. There are additional advantages due to the system being compact, lightweight, and highly corrosion resistant.Implications: This study focused on integrating and assessing performance of a novel hybrid composite electrode (HCE) inside semi-pilot novel cross-flow electrostatic precipitator at conditions typically observed in coal-fired power plant exhausts. The results were collected for particulate collection efficiencies and were compared with a rigid metal electrode. The HCE outperformed metal electrode by showing higher particulate collection efficiency. This result showcases substantial potential for these two new technologies (HCE and cross-flow system) as a substitute for conventional metal based wet ESPs.

(Invited) Study on the Degradation of PEM Water Electrolysis MEA after Long-Term Operation

Water electrolysis has the potential to become a key element in coupling the electricity, mobility, heating and chemical sector via power-to-liquids or power-to-gas in a future sustainable energy systems [1]. While proton exchange membrane (PEM) water electrolysis offer several advantages over traditional electrolysis technology, advances are still needed in catalyst stability against corrosion and fluctuated loads for PEM water electrolysis [2]. In particular, the anode requires improvement in the activity and stability of the catalyst due to the sluggish kinetics of oxygen evolution reaction (OER) and the corrosive environment due to high overpotentials. The state-of-the-art anode catalyst in conventional PEMWEs is iridium oxide. However, iridium suffers from dissolution at high anodic potentials [3] albeit being the most corrosion resistant metal known. The iridium dissolution in a MEA is evidenced by the iridium deposits in the electrolyte membrane [4, 5]. Furthermore, platinum degradation on the cathode has been reported where platinum nanoparticles were coarsened after long-term operation [6, 7]. Although the platinum coarsening is not directly related to the cell potential increase after long-term operation, the stability of the platinum nanoparticles is important in the context of reducing the platinum loading [6]. In this study, post mortem MEAs are analyzed with electron microscopy to investigate the degradation mechanisms and to provide guidance for future electrode design. The full MEA was fabricated by reactive spray deposition technology (RSDT) with ultra-low iridium and platinum loading. The anode catalyst is composed of IrOx nanoparticles embedded in Nafion ionomer with an iridium loading of 0.08 mg cm-2; while the cathode is platinum supported on carbon black with a platinum loading of 0.3 mg cm-2. These loadings are about 10% of the loadings that are currently used in state-of-the-art electrolyzers. The full RSDT-derived MEA successfully demonstrated a long-term operation of 4500 hours. Preliminary study on the anode catalyst degradation shows that the anode catalyst layer thickness is reduced by 15% due to compression and/or loss of iridium catalyst (Figure 1a, b). In addition, metallic iridium deposits are found in the electrolyte membrane adjacent to the anode catalyst for the post mortem MEA cross section (Figure 1c, d). EDX mapping of the deposits confirm the metallic state of iridium (Figure 1 e, f). Further analysis of the post mortem MEA cross section will elucidate through-plane catalyst loading distribution using high-resolution TEM and EDX analysis, for both anode and cathode.

Numerical simulation of fatigue life of 2A02 aluminum alloy treated by overlapping laser shock processing

Laser shock processing (LSP) has been now recognized as an efficient surface strengthening technology to improve fatigue, corrosion and wear resistance of metals. In this paper, the effect of residual stress on the fatigue life of 2A02 aluminum alloy specimens subjected to LSP was investigated by the finite element method (FEM). This investigation was split into two parts, numerical simulation of the LSP process and the fatigue analysis. The LSP simulation was performed using the commercial code ABAQUS. The fatigue analysis, using the residual stresses obtained in the previous LSP simulation as input, was performed by the commercial node nCode Designlife. The simulation results indicate that under the fatigue loading of maximum axial stress of 365MPa and the stress ratio of R=0.1, the fatigue life of specimens with LSP was extended up to 205.7% from 12,290 times to 25,280 times. It was observed that the residual compressive stresses induced by LSP can significantly prolong the fatigue life of 2A02 aluminium alloy specimens. It is found that simulation results are well agreement with available experimental data. It indicate that FEM calculation of specimen life with LSP is feasible.

Investigation of metallurgical and mechanical properties of 21st century nickel-based superalloy 686 by electron beam welding technique

Electron Beam Welding (EBW) was performed on the highly corrosion resistance superalloy 686. The present research work investigates the metallurgical and mechanical properties of the weld joint fabricated by Electron Beam Welding technique, and the results are compared with the base metal. Optical and Scanning Electron Microscope (SEM) analysis were carried out to study the structural properties of the weld joint. The fine equiaxed dendritic structure was revealed in the Center Fusion Zone (CFZ). The columnar dendrite was noticed in the Transition Fusion Zone (TFZ). Energy-dispersive X-ray spectroscopy (EDS) analysis results show that segregation of Mo and W were noticed in the sub-grain boundary. X-ray diffraction analysis (XRD) confirmed the presence of Mo and W rich phases in the weldment. Tensile testing was carried out to evaluate the strength and ductility of the weld joint. The result revealed that the weld strength was equal to the base metal strength. The presence of Mo and W-rich intermetallic phase reduced the ductility and toughness of the weld joint compared to base metal. Bend test confirmed the defect-free weld joint that was achieved in the Electron Beam Welding technique. The corrosion rate of base metal and EBW weldment are calculated in the synthetic seawater environment with the help of Potentiodynamic polarization experiment, and corrosion rate is measured with Tafel’s interpolation technique. The corrosion test result shows that the resistance of EBW weldment is lesser than base metal corrosion resistance because of the microsegregation of alloying elements in the interdendritic region.

A one-dimensional time-dependent model for studying oxide film growth on metallic surfaces

Corrosion resistance of industrial metals and alloys is largely imparted by the formation of a stable oxide film on the surface that kinetically limits the process of corrosion. Developing a fundamental knowledge of the processes involved in the oxide layer formation and growth is thus important for designing corrosion-resistant alloys. In this work, a model for oxide growth tracking two species (the oxygen and metal vacancies) was presented. The model accounted for species transport and interfacial chemistry. The potential profile was obtained by solving the Poisson equation without needing to invoke the typical linear assumption. Moreover, the fully time-dependent concentration and potential profiles were obtained and the oxide thickness was allowed to evolve by allowing the movement of the domain boundaries at either end. The results were analyzed and the effects of different parameters on the model were discussed.

Effect of Rare-Earth Elements on the Corrosion Resistance of Flux-Cored Arc-Welded Metal with 10CrNi3MoV Steel

We modified the content of rare-earth elements (REE) in the flux-cored wire used to produce welds of high-strength low-alloy (HSLA) steel. The effect of REE addition on the microstructure as well as on the mechanical and electrochemical properties of the welded metal (WM) was investigated. REE-modified welded metals show very different responses during electrochemical impedance spectroscopy and the potentiodynamic polarization tests. The results indicate that the addition of REE of 0.3 wt.% facilitates a more uniform microstructure and improves both mechanical properties and corrosion resistance in welded metals.

Lubricant-infused coating by double-layer ZnO on aluminium and its anti-corrosion performance

In this study, double-layer zinc oxide was synthesized on an aluminium substrate by combining a sol-gel and a hydrothermal method. The bottom layer was flower-like and the upper layer was rod-shaped. The aluminium sheet coated with zinc oxide was infiltrated into a lubricating oil for 2 h to obtain an aluminium-based double-layer ZnO super-slippery surface. Testing showed that the surface demonstrated a good anti-fouling effect. The coating was hydrophobic and oleophobic, and even fruit juice and jam slipped down the surface at a small tilt angle (<5°). The corrosion resistance was also four orders of magnitude higher than that of the untreated aluminium sheet, and after three months, the anti-corrosion performance did not change significantly. Such good performance in the metal's corrosion resistance provides numerous potential application prospects.

An electrochemical method based on OCP fluctuations for anti-corrosion alloy composition optimization

Purpose An electrochemical method based on the open circuit potential (OCP) fluctuations was put forward. It can be used to optimize the alloy compositions for improving the corrosion resistance of rust layer. Design/methodology/approach The potential trends and potential fluctuations of carbon steels in seawater were separated by Hodrick–Prescott filter. The Spearman correlation coefficient and max information coefficient were used to explore the correlation of alloy compositions and potential fluctuations. Findings After long-term immersion, potential fluctuation resistance (PFR) can be used to characterize the corrosion resistance of metals and its rust layers. In the 1,500 to 2,500 h exposure period, Fe, C and S compositions have strong negative correlations, whereas PFR and P composition have weak negative correlations. Mn, Cu and Ti alloy compositions help the rust layer of carbon steels have higher PFRs. These elements that exhibit higher PFRs in this period have been confirmed to have the effect on improving the corrosion resistance of rust layer. Originality/value A new computing method for alloy composition optimization of carbon steels based on the OCP fluctuations was put forward. This method combines electrochemical monitoring with the long-term actual seawater environmental tests of various carbon steels.

Corrosion behavior analyses of metallic membranes in hydrogen iodide environment for iodine-sulfur thermochemical cycle of hydrogen production

HI decomposition in Iodine-Sulfur (IS) thermochemical process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion as well as highly corrosive environment. Corrosion-resistant metal membrane reactor is proposed to be a process intensification tool, which can enable efficient HI decomposition by enhancing the equilibrium conversion value. Here we report corrosion resistance studies on tantalum, niobium and palladium membranes, along with their comparative evaluation. Thin layer each of tantalum, palladium and niobium was coated on tubular alumina support of length 250 mm and 10 mm OD using DC sputter deposition technique. Small pieces of the coated tubes were subject to immersion coupon tests in HI-water environment (57 wt% HI in water) at a temperature of 125–130 °C under reflux environment, and simulated HI decomposition environment at 450 °C. The unexposed and exposed cut pieces were analyzed using scanning electron microscope (SEM), energy dispersive X-ray (EDX) and secondary ion mass spectrometer (SIMS). The extent of leaching of metal into liquid HI was quantified using inductively coupled plasma-mass spectrometer (ICP-MS). Findings confirmed that tantalum is the most resistant membrane material in HI environment (liquid and gas) followed by niobium and palladium.

쇼트피닝 가공 Ti-6Al-4V의 추가 표면 가공에 따른 부식 저항

Ti-6Al-4V has been used as an implant material because of its high toughness, high strength, low density, and strong corrosion resistance. However, ions and proteins present in the human body accelerate the corrosion of implant materials. Shot peening is one of the simplest ways to induce compressive residual stress on the metal surface, which has a positive effect on the fatigue life and corrosion resistance of metals. The surface of implants inserted into the body, such as knee joints, needs to be smooth to reduce frictional wear. Therefore, in this study, the surfaces of coin-sized specimens were grinded after a shot peening process. Then, an accelerated corrosion test was performed by supplying a constant current (5 mA) to the specimen, in normal saline, for one hour. The results show that the shot peening process improves corrosion resistance, and the corrosion depth depends on the degree of surface treatment.

“Nickel Nanoflowers” with Surface-Attached Fluoropolymer Networks by C,H Insertion for the Generation of Metallic Superhydrophobic Surfaces

Metallic superhydrophobic surfaces (SHSs) combine the attractive properties of metals, such as ductility, hardness, and conductivity, with the favorable wetting properties of nanostructured surfaces. Moreover, they promise additional benefits with respect to corrosion protection. For the modification of the intrinsically polar and hydrophilic surfaces of metals, a new method has been developed to deposit a long-term stable, highly hydrophobic coating, using nanostructured Ni surfaces as an example. Such substrates were chosen because the deposition of a thin Ni layer is a common choice for enhancing corrosion resistance of other metals. As the hydrophobic coating, we propose a thin film of an extremely hydrophobic fluoropolymer network. To form this network, a thin layer of a fluoropolymer precursor is deposited on the Ni substrate which includes a comonomer that is capable of C,H insertion cross-linking (CHic). Upon UV irradiation or heating, the cross-linker units become activated and the thin glassy film of the precursor is transformed into a polymer network that coats the surface conformally and permanently, as shown by extensive extraction experiments. To achieve an even higher stability, the same precursor film can also be transformed into a chemically surface-attached network by depositing a self-assembled monolayer of an alkane phosphonic acid on the Ni before coating with the precursor. During cross-linking, by the same chemical process, the growing polymer network will simultaneously attach to the alkane phosphonic acid layer at the surface of the metal. This strategy has been used to turn fractal Ni "nanoflower" surfaces grown by anisotropic electroplating into SHSs. The wetting characteristics of the obtained nanostructured metallic surfaces are studied. Additionally, the corrosion protection effect and the significant mechanical durability are demonstrated.

Composition-controlled active-passive transition and corrosion behavior of Fe-Cr(Mo)-Zr-B bulk amorphous steels

Various corrosive environments in daily life and industry have put forward high requirement on corrosion resistance of metals, especially steels. Unlike the strict demand in Cr content of crystalline stainless steels, amorphous steels (ASs) with lower Cr content can be endowed with outstanding corrosion resistance, while the intrinsic mechanism is not fully understood. Herein, we present a novel Fe92−x−y−zCrxMoyZr8Bz (6 ≤ x ≤ 40, 0 ≤ y ≤ 22, and 12 ≤ z ≤ 18) bulk amorphous steel (BAS) forming system and reveal the synergistic effect of Cr and Mo in determining the chemical stability of oxide films. It has been found the Fe92−x−zCrxZr8Bz BASs with 1 mm in diameter display a Cr-controlling active-passive transition at the Cr threshold of ∼25% in 1 M hydrochloric acid. When adding minor Mo into the BASs, the Cr threshold can be remarkably reduced by forming favorable hexavalent Mo oxides. The generation of Mo6+ is facilitated by atomic selective dissolution at the interface and can promote the passivation. In contrast, when the Cr content of the Mo-doped glasses exceeds 25%, few Mo6+ oxides would produce as the prior formation of protective passive films inhibits the further oxidation of Mo. Therefore, manipulating the active-passive transition properly is crucial to designing ASs with high stainlessness.

Corrosion Behaviour and Characterization of Thermal Sprayed Coating of Nickel Chromium Cermet on Low Carbon Steel

Corrosion is the major problem faced by Navy, especially when pumps, ship impellers and other components have to work in harsh environments like sea water. Therefore, high corrosion resistant metal ceramic matrix 75Cr3C2- 25 (NiCr) cermet has been one of the good choices for coating. In this study, we are discussing the HVOF (High Velocity Oxy Fuel) coating of 75Cr3C2-25(NiCr) on the low carbon steel substrate, IS 2062 grade B. The as coated samples were annealed at 600°C for 1 hour, 2hour and 3hours. The electrochemical tests were conducted for corrosion evaluation. Structural analysis was done by using X-Ray diffraction technique. Microstructure and thickness of the coating was studied using Scanning Electron Microscopy (SEM). Density measurement studies were done on as-coated and annealed coupons.

Influence of rare earth ions on metal ions distribution and corrosion behavior of tailing-derived glass-ceramics

In understanding the influence of rare earth ions on crystallization, metal ions distribution, crack propagation and corrosion resistance of tailing-derived glass-ceramics, CeO2 containing glass-ceramics were prepared by melting method. Decrease of degree of crystallization of glass-ceramics with the increase of CeO2 content was maintained by the intensified stabilization of glass structure owing to the high electric field characteristics of Ce4+. A significant change in metal ions distribution can be observed in glass-ceramics with the increase of CeO2 content, which can result in the formation of aggregates. The aggregation induced by rare earth doping had a certain inhibiting effect on the propagation of cracks. In addition, the acid-resistance of glass-ceramics had been improved. The densification of the glass phase induced by the high field of Ce4+ was beneficial to the performance improvement.

Effect of PLLA coating on corrosion and biocompatibility of zinc in vascular environment

Zinc (Zn) has recently been introduced as a promising new metal candidate for biodegradable vascular stent applications with a favorable degradation rate and biocompatibility. Corrosion-resistant metal stents are often coated with drug-eluting polymer layers to inhibit harmful biological responses. Here, the authors aimed to investigate the interaction between biodegradable zinc metal and a conventional biodegradable polymer coating. Zinc wires with a diameter of 0·25 mm were surface-modified using 3-(trimethoxysilyl)propyl methacrylate (MPS) and then coated with a 1–12 μm film of poly(l-lactic acid) (PLLA). The corrosion behavior of PLLA/MPS-coated zinc wires was studied in simulated body fluid using electrochemical impedance spectroscopy. An increase in the impedance from &lt;1000 to &gt;15 000 Ω cm2 was recorded for the zinc wires after being coated with PLLA. The PLLA/MPS-coated zinc specimens were implanted into the abdominal rat aorta to assess their biodegradation and biocompatibility compared to uncoated zinc wires. PLLA/MPS-coated wires corroded at approximately half the rate of unmodified zinc during the first 4·5 months. A histological analysis of the biological tissue surrounding the zinc implants revealed a reduction in the biocompatibility of the polymer-coated samples, as indicated by increasing cell toxicity and neointimal hyperplasia.

Niobium alloys for the chemical process industry

Tantalum materials have been used extensively in some of the most demanding applications in the chemical process industry (CPI) for many years. However, tantalum and tantalum alloys are not only expensive relative to other corrosion resistant metals such as zirconium, but can be considered excessive for many less demanding applications. Niobium is used on a limited basis in the CPI due to its low mechanical strength and poor corrosion resistance relative to tantalum and zirconium. Consequently H.C. Starck undertook a project to develop new niobium alloys with improved corrosion resistance as well as improved mechanical properties. Initial results have shown these niobium alloys have corrosion resistance significantly improved over pure niobium and zirconium with mechanical properties comparable to Ta-3W, the standard tantalum based CPI alloy.

Corrosion of titanium: Part 2: Effects of surface treatments.

Titanium is well known as one of the most corrosion-resistant metals. However, it can suffer corrosion attacks in some specific aggressive conditions. To further increase its corrosion resistance, it is possible either to modify its surface, tuning either thickness, composition, morphology or structure of the oxide that spontaneously forms on the metal, or to modify its bulk composition. Part 2 of this review is dedicated to the corrosion of titanium and focuses on possible titanium treatments that can increase corrosion resistance. Both surface treatments, such as anodization or thermal or chemical oxidation, and bulk treatments, such as alloying, are considered, highlighting the advantages of each technique.

Pengaruh Perlakuan Panas Quenching dan Tempering terhadap Laju Korosi pada Baja AISI 420

&lt;p&gt;Corrosion occurs in almost all metals. Even corrosion-resistant metals are corroded, but their corrosion rate is different from ordinary or non-corrosion resistant metals. This study examines the corrosion rate that occurs in stainless steel that is stainless steel. Stainless steel contains high enough chromium levels that can reduce the rate of corrosion that occurs. The metal material to be studied is the AISI 420 steel, which belongs to the Martensitic Stainless Steel class. This study examined the effect of heat treatment on corrosion rate and hardness level of AISI 420 steel. The heat treatment carried out was Quenching at 1020&lt;sup&gt;o&lt;/sup&gt;C with a holding time of 60minutes with an oil cooling medium. After quenching the subsequent heat treatment is tempering with temperature variations of temperature 200&lt;sup&gt;o&lt;/sup&gt;C and 300&lt;sup&gt;o&lt;/sup&gt;C with a resistance time of 45 minutes and air cooling media. The results of this study showed that the base material specimens had the highest corrosion rate of 0.569 mm/y. The lowest corrosion rate is in specimens with quenching process with a value of 0.267 mm/y. The highest Vickers hardness values were found in specimens with quenching process with a value of 551 kg/mm&lt;sup&gt;2&lt;/sup&gt;. The lowest hardness value is in the specimen with tempering process at 300&lt;sup&gt;o&lt;/sup&gt;C with 405 kg/mm&lt;sup&gt;2&lt;/sup&gt;.&lt;/p&gt;

CeO2 modified SiO2 acted as additive in electrodeposition of Zn-Ni alloy coating with enhanced corrosion resistance

Recently, rare earth oxide has attracted much attention because of its widely applications in petroleum, chemical engineering, metallurgy, ceramics etc. Among them, ceria has been considered as an important additive to improve metal's corrosion resistance. In this study, CeO2 modified SiO2 was prepared as additive in electrodeposition of Zn-Ni coating. The state of the as-prepared particles was characterized. The structure and wettability as well as the microhardness of coatings were tested. Moreover, the corrosion performance of coatings was analyzed in detail by means of potentiodynamic polarization technique and electrochemical impedance spectrum (EIS) in 3.5 wt % NaCl solution which used as corrosion medium. The results show that the particles disperse well among the coatings. The morphology of the coating presents a dense structure and keeps a highly preferred orientation. Meanwhile, the coating with CeO2 modified SiO2 exhibits much better corrosion resistance properties compared with that of both Zn-Ni and Zn-Ni-SiO2 coatings. The corrosion current density of the prepared coating was remarkably decreased with two and one orders of magnitude compared with those two CeO2-free coatings mentioned above, respectively. The introduction of CeO2 also significantly increases the coating's electrochemical impedance. The corrosion mechanism of the above three types of coating on low carbon steel were analyzed and discussed based on two different equivalent circuit models respectively.

Effect of Nonmetallic Inclusions and Impurities on the Properties and Quality Characteristics of Round Rolled Product Made of Special Alloyed Steels

It is found from results of studying rolled steel from special alloyed steels of industrial grades 30G1R, 40Kh and laboratory grades 12KhN, 38KhGNM, 41Kh1 that a change in the ratio of Mn:S concentration in the range of 21–620, P content from 0.004 to 0.022 wt.%, non-metallic inclusions up to point 2.5 according to GOST 1778, N up to 0.010%, H up to 0.0005%, with total pressure created by gas-forming elements up to 1.05 atm, are not critical for occurrence of defects and rolling capacity for cold upsetting. Determination of the characteristics of NI, and CANI content in steel 40Kh round rolled product shows that metal corrosion resistance increases by more than a factor of three with a reduction in CANI2 content and inclusions of the system CaO–Al2O3–MgO containing up to 5 wt.% SiO2, and the insignificant effect of other types of inclusions. A study of the metal of high-strength fasteners manufactured by JH (Taiwan), OF, AL (USA) shows that it has a significantly lower content of other types (corundum, calcium, aluminate, sulphide) of inclusions, and conversely better corrosion resistance.