The pre-oxidation process of electropolishing for the textured {113} <121> Ag substrate for Tl-1223 superconductor substrate

The surface roughness of a substrate is typically influenced by grain boundaries, grooves and voids. In an effort to improve the surface roughness, a textured {113} <121> Ag substrate was electropolished using a new method that causes the formation of an oxidation layer at the constant current density before electropolishing at a constant voltage of 1.75 V vs. SCE. The constant current density and potential were determined using the anodic polarization method. The pH effect for the optimized electropolishing condition was also investigated by adding phosphoric acid. The edges of the grain boundaries, grooves and voids became smoother when a constant current density was supplied with the pre-oxidation. A RMS (root mean square) value of 5.90-nm regarding the surface roughness of the Ag substrate was obtained without a final surface treatment before electropolishing, while a RMS surface roughness value of 34.12-nm was obtained for an Ag substrate that was given a final surface treatment for mechanical polishing.     

Electropolishing parameters of NiTi alloy

Electropolishing has been used in NiTi alloy in several fields for its special characteristics, but its essential details and electropolishing mechanism have not been reported yet as a demand from business competition, which, to a great degree, restricts the application and extension of the electropolishing technology. The effect of processing parameters on nitinol electropolishing was explored. Besides the electrolyte, other factors that influence the electropolishing are temperature, current density, time, spacing between anode and cathode, electrolyte stirring, etc. Studies on the effect of the temperature on the electropolishing process show that the higher the temperature is, the bigger the electropolishing rate is, following the near Gauss law. The relationship between the temperature and the surface roughness follows a near parabolic law, and the relationship between the temperature and the surface reflectivity follows a near sigmoidal law. The relationship between the electropolishing voltage and the current density follows a near cubic law, while that between the electropolishing rate and current density follows a near linear law. The relationship between the electropolishing rate and the time follows a near sigmoidal law. The practical spacing between anode and cathode is confirmed by the Hall bath experiment.     

Corrosion of biomaterials: anodic treatment and evaluation of 316L stainless steel in simulated body fluid

The influence of electropolishing at different conditions on the electrochemical behaviour of 316L stainless steel (316L SS) in simulated body fluid (SBF) was investigated. Accordingly, 316L SS samples were electropolished in several electropolishing baths of H₃PO₄ and H₂SO₄ at 2–6 applied volts and 50–110°C for different time intervals. The corrosion behaviour then was studied by means of potentiodynamic polarisation technique and electrochemical impedance spectroscopy in SBF at 37°C. The surface morphology was also investigated by scanning electron microscopy. The results proved that the treated samples had better corrosion resistance than nonpolished one. The highest corrosion resistance was observed for the treated sample at 5?V and 90°C in 10:90 ratio of acidic electrolyte (H₃PO₄:H₂SO₄) for 15?min. Moreover, the corrosion resistances of anodically treated samples were found to be dependent greatly on applied volt, bath temperature, polishing time and phosphoric to sulphuric acids ratio.     

Morphological and Microstructural Aspects of Metal Dusting on 304L Stainless Steel with Different Surface Treatments

The effect of surface treatment on the susceptibility to metal dusting of 304L stainless steel (SS) exposed in a mixed gas of CO/CO₂ = 100/1 in the temperature ranging from 500–700 °C was investigated. Thermogravimetric analyses (TGA) and long-term exposure tests in the above environments, followed by surface-morphological examination and cross-section chemical composition and microstructure analyses were conducted. The results showed that the decomposition of CO gas to form graphite and nano-sized carbon filaments was affected by the surface pre-treatment applied on the 304L SS. Enhanced carbon deposition but with a significant resistance to metal dusting was found on the sand-blasted 304L SS. The existence of an initial non-protective oxide on the pre-oxidized 304L SS surface, however, gave rise to the highest susceptibility to metal-dusting-associated-localized attack. The roles of different surface treatments on the reactions between 304L SS and the exposing gas environment are discussed.     

Surface characterization of AISI 316L biomaterials obtained by electropolishing in a magnetic field

The paper deals with comparison of the results obtained by electropolishing AISI 316L surfaces in an externally applied magnetic field with those of a standard electropolishing process. All electrochemical investigation methods, electrochemical impedance spectroscopy (EIS), polarization curve measurements, and surface analytical methods such as surface roughness measurements and scanning electron microscopy were carried out to determine the efficacy of electropolishing in a magnetic field.     

Electropolishing of AISI-304 stainless steel for protection against SRB biofilm

Electropolishing treatment (EP) can be used to remove the biofilm formed on AISI-304 stainless steel surface and protect it against bacterial colonization. High levels of both smoothness and brightness of AISI-304 stainless steel surfaces can be attained by using electropolishing technique, where the sample was fixed as anode and a suitable current was applied into electrolytic cell containing H₃PO₄. AISI-304 stainless steel was exposed to stabilized mixed culture of sulfate reducing bacteria (SMC-SRB) under different conditions as, temperature, pH, salinity, incubation time and inoculum size. The present study recorded the main indicators of bacterial activity such as S⁻⁻, Fe⁺⁺, most probable number (MPN) of SRB and weight loss (corrosion rate) by milinches per year (mpy). The results revealed that the bacterial counts were obviously decreased under all conditions of bacterial biofilm formation after electropolishing treatment.     

The effects of electropolishing (EP) process parameters on corrosion resistance of 316L stainless steel

Improvement of the corrosion resistance capability of a workpiece being processed by the electropolishing (EP) is one of the most importance process characteristics. In this paper, the effects of the EP process parameters on the corrosion resistance performance of the SS 316L stainless steel were studied based on the uniform and localized intergranular corrosion (IGC) analyses. The IGC is the prominent characteristics of localized corrosion in stainless steel.

The workpiece (anode) material was the SS 316L stainless steel. The cathode material under study was platinum. The electrolyte was composed of sulfuric acid, phosphoric acid, glycerin and DI water. The test specimens were all polished before experiments in order to reduce the effect of the bailby layer. Variables of the EP process parameters gap between the electrodes and the process time.

The specimens were analyzed, first, by the surface roughness measurement. Secondly, they were observed under the optical microscope for surface marks and defects. It was followed by the linear polarization analysis for the uniform corrosion performance. The electrochemical potentiokinetic repassivation (EPR) test was employed to study the localized, IGC. Finally, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses were conducted to analyze the metallurgical composition and the thickness of the passive film. The results showed that the EP process greatly improved the corrosion resistance of the SS 316L stainless steel.     

Electrosynthesis of Poly(ortho-phenetidine) Coatings on Steel and Investigation of Their Corrosion Protection Properties

Poly(ortho-phenetidine) coatings on 304 stainless steel (304 SS) surface have been synthesized by using the galvanostatic technique. The electrosynthesized coatings were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), UV-visible absorption spectrometry and Scanning Electron Microscopy (SEM). The anticorrosion performances of poly(ortho-phenetidine) coatings were examined in 0.1 M HCl medium by the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization technique. The corrosion rate of poly(ortho-phenetidine)-coated 304 SS was found ~10 times lower than bare 304 SS and corrosion potential increased from –0.29 V for uncoated 304 SS to –0.19 V versus Ag/AgCl (3 M KCl) for poly(ortho-phenetidine)-coated 304 SS electrode. Electrochemical measurements indicate that poly(ortho-phenetidine) coating has good inhibiting properties with an efficiency of ~93% at 1.5 mA cm^–2 applied current density in acidic corrosive media. The results of this study obviously ascertain that the poly(ortho-phenetidine) has an outstanding potential to protect 304 SS against corrosion in an acidic environment.     

304不锈钢复合电镀镍-膨胀石墨导热性能

通过一种简单而经济的电镀方法在304不锈钢表面制备镍-膨胀石墨复合材料,并对其导热性能进行研究。通过扫描电子显微镜(SEM)、拉曼光谱(Raman)、X射线衍射(XRD)和能谱仪(EDS)对镀层的显微形貌及结构进行表征,通过激光粒度分布仪对膨胀石墨的粒径进行测定,通过激光导热仪测定复合镀层的导热系数。结果表明:膨胀石墨呈片状结构,缺陷少且复合镀前后缺陷基本不变。复合镀层中膨胀石墨的原子数分数为5.98%,且均匀分布。镍-膨胀石墨/304不锈钢的导热系数为16.02 W/(m·K),相比于镍/304不锈钢和304不锈钢,其导热系数分别提高了9.7%和23.8%。膨胀石墨与304不锈钢表面及镍镀层接触良好,构成了良好的导热通道,提高了镍镀层的导热性能。     

Electropolishing of nickel and cobalt in deep eutectic solvents

Electropolishing is a common method for decreasing surface roughness and removing surface irregularities. In this paper the electropolishing of nickel and cobalt are successfully demonstrated in a deep eutectic solvent, comprising a 2:1 molar mixture of ethylene glycol and choline chloride. Voltammetric and electrochemical impedance studies were used to characterise the polishing mechanism and show that film formation occurs prior to polishing. Scanning electron microscopy and atomic force microscopy were used to characterise the morphology before and after polishing and 3D optical microscopy was used in-situ to observe film formation during polishing. This study shows that the impact of film formation and subsequently mass transport are responsible for electropolishing of both metals in the choline chloride-based ionic liquid.     

304不锈钢表面单层/多层TiN基涂层制备及耐磨蚀性能研究

目的探究钢基表面TiN基涂层在海洋环境中的耐磨蚀性能。方法采用电弧离子镀技术,在304不锈钢和单晶硅表面分别沉积TiN、TiBN、TiBN/TiN涂层,并对3种涂层样品的表面–截面形貌、摩擦系数、在人工海水中的电化学性能和摩擦腐蚀行为进行测试。结果形貌表征和干摩擦测试结果显示,TiBN和TiBN/TiN涂层有着比TiN柱状晶更加致密的微观结构,3种涂层的摩擦系数相差不大,比304SS的摩擦系数低。在人工海水环境中的电化学测试结果表明,TiBN/TiN涂层的耐腐蚀性能最佳,TiBN涂层次之,TiN涂层则表现出比304不锈钢基底更差的耐腐蚀特性。在发生摩擦腐蚀的过程中,3种涂层的电位（OCP）均发生了下降。结论利用电弧离子镀技术在304不锈钢表面沉积的单层/多层TiN基涂层,在人工海水环境下,发生的摩擦会增加涂层发生腐蚀的趋势,结构致密,表面易形成钝化膜的涂层,其耐磨蚀性较好。     

轧制纳米块体304不锈钢腐蚀行为的研究Ⅱ钝化膜保护性能

采用动电位极化曲线和Mott-Schottky分析等电化学测试手段,探讨了轧制纳米块体304不锈钢与普通304不锈钢在0.05mol/L H2SO4＋0.05mol/L Na2SO4溶液中钝化膜的保护性能;运用点缺陷（PDM）模型,分析了不同电位下在0.05mol/L H2SO4＋0.25mol/L Na2SO4溶液中两种材料形成钝化膜的半导体性质,阐述了导致两种钝化膜保护性能差异的根本原因.结果表明：两种材料表面钝化膜都具有n型半导体特征,氧空穴作为主要的载流子参与钝化膜的形成和溶解过程;钝化膜中载流子密度与钝化膜的形成电位之间满足幂指数关系,载流子在两种材料表面的钝化膜中的扩散系数非常接近,说明两种钝化膜遵从相似的形成和溶解机制,但轧制纳米块体304不锈钢中的载流子密度小于普通304不锈钢钝化膜中的载流子密度,从而使其钝化膜具有更好的保护性.     

The Electropolishing of Chromium and Its Alloys

A technique for electropolishing chromium and chromium-based alloys has been devised. The polishing baths contain orthophosphoric acid, sulphuric acid and water, or orthophosphoric acid alone. Conditions are given for obtaining rapid smoothing, polishing and electroetching of the surface for metallographic examination. The probable mechanisms of electropolishing, and of anodic passivity on chromium in the polishing bath, are discussed.     

模板用冷轧304不锈带钢表面硬度及粗糙度的控制

针对模板用304不锈带钢多依赖进口,急需实现国产化的现状,太原钢铁(集团)有限公司对其进行了研发.该品种需满足一定的表面硬度及表面粗糙度要求.通过理论分析及现场实践,采用加工硬化及细晶强化的措施来提高304不锈带钢的硬度,当采用20％～40％的冷轧变形量,以及800～1 000℃退火温度时,可消除304不锈带钢铁磁性且...     

Corrosion of aluminium,stainless steels and AISI 680 nickel alloy in nitrogen‐based fuels

Nitrogen‐based compounds can potentially be used as alternative non‐carbon or low‐carbon fuels. Nevertheless, the corrosion of construction materials at high temperatures and pressures in the presence of such fuel has not been reported yet. This work is focused on the corrosion of AISI Al 6061, 1005 carbon steel (CS), 304, 316L, 310 austenitic stainless steels (SS) and 680 nickel alloy in highly concentrated water solution of ammonium nitrate and urea (ANU). The corrosion at 50 °C and ambient pressure and at 350 °C and 20 bar was investigated to simulate storage and working conditions. Sodium chloride was added to the fuel (0–5 wt%) to simulate industrial fertilizers and accelerated corrosion environment. Heavy corrosion of CS was observed in ANU solution at 50 °C, while Al 6061, 304 and 316L SS showed high resistance both to uniform and pitting corrosion in ANU containing 1% of sodium chloride. Addition of 5% sodium chloride caused pitting of Al 6061 but had no influence on the corrosion of SS. Tests in ANU at 350 °C and 20 bar showed pitting on SS 304 and 316L and 680 nickel alloy. The highest corrosion resistance was found for SS 310 due to formation of stable oxide film on its surface.     

Effect of copper on metal dusting of austenitic stainless steels

Three steels, 304SS, 310SS and 800H, were alloyed with 5%, 10%, and 20% (by weight) copper, and then exposed to 68%CO-31%H₂-1%H₂O gas at 680 °C (a_C = 19 and p_O2=5.4×10^-25 atm) under thermal cycling conditions. Kinetic measurements showed that copper-free alloys all dusted, with 304SS experiencing the greatest metal wastage. Copper additions did not have any effect on metal wastage of 304SS, but reduced the attack on 310SS and 800H markedly at levels of 5% and 10%. However, increasing the copper content to 20% produced large copper-rich precipitates which accelerated dusting by promoting internal graphitisation.Dusting was associated with surface coking. When pitting occurred, on copper-free alloys and on copper containing 304SS, large coke structures grew above the pits. Internal grain boundary carburisation always took place, and intragranular carbides also precipitated when dusting occurred. A lamellar surface layer of internally precipitated spinel and austenite also developed in association with dusting. The copper effect is discussed in terms of its alloy solubility and its known beneficial effect in Ni-Cu binaries.     

Magnetoelectropolishing for metal surface modification

Abstract

This paper aims to present the preliminary results of magnetoelectropolishing, a process derived and named by application of an external magnetic field coupled with the process being controlled and maintained under oxygen evolution to achieve an electropolished surface of a workpiece. The obtained surfaces exhibit reduced microroughness, better surface wetting resulting from increased surface energy, reduced and more uniform corrosion resistance, minimisation of external surface soiling and improved cleanability. The externally applied magnetic force for use with the enhanced electropolishing process may be selected from a group consisting of either permanent magnetic or electromagnetic devices. It has been shown that the enhanced electropolishing process results in better surface performance. In the present paper, for comparison purposes, results of surface roughness, hydrophilicity and corrosion behaviour are presented. Further studies, concerning the corrosion characteristics, the morphology and surface film chemistry, are in progress.     

带锈铸铁与304不锈钢的电偶腐蚀

研究了在3.5% NaCl溶液中带锈铸铁和304不锈钢(SS3 04)之间的电偶腐蚀效应和特性,以及面积比对电偶腐蚀效应的影响.结果表明,SS304(面 积为Ac)与带锈铸铁(面积为Aa)面积比S(Ac/Aa)≤16时,电偶电流大小取决于SS304 表面在耦合电位时的阴极反应速率;随着面积比S的增大,电偶电流密度Ig/Aa 增大,但Ig/Ac降低,而且受限于SS304表面氧扩散极限电流密度;随面积比S 的增大,电偶腐蚀效应增大,但相对来说,电偶腐蚀效应是较小的.面积比S太大时,可能 使本身为钝化态的SS304在偶接活化后发生阴极腐蚀.建议S≤4.     

Oxidation behavior of TiC particle-reinforced 304 stainless steel

TiC particle-reinforced 304 stainless steels were prepared using a new developed in situ technology and exhibited the uniform distribution of TiC particles in the matrix. The oxidation behavior of 304SS-2TiC and 304SS-6TiC (all in weight percentage) was compared with that of 304SS at 850 °C in air for 96 h using thermogravimetry analysis. For 304SS, the rate of weight gain was very slow initially, but accelerated suddenly to a very high level, forming breakaway oxidation. The addition of TiC particles to 304SS resulted in no breakaway oxidation and maintained a low oxidation rate in the whole reaction time investigated. Examination of oxide scale morphology and cross-section analysis by scanning electron microscopy and optical microscopy showed a significant scale spallation and a deep oxide penetration in the case of 304SS, but a rather continuous, dense and adherent oxide layer formed on the surface of TiC particle-reinforced alloys. XRD analysis revealed the presence of Cr₂O₃ together with spinel-type oxides in the oxide scale. For TiC-containing alloys, fine TiO₂ was also found on the surface and the amount of this oxide increased with TiC addition. The TiC addition developed finer matrix structure before oxidation, which accelerates chromium diffusion. As a result, scale adherence was improved and oxidation resistance was increased.     

Microstructural characterization of superaustenitic stainless steel surface alloys formed using laser treatment

Conventional stainless steels (SS’s) such as AISI type 304 SS are used in many industrial applications due to their excellent weldability and good mechanical properties. However, in contacts with chlorides, they suffer from localized corrosion. AISI type 304 SS was alloyed at the surface with chromium, nickel, and molybdenum using a CO₂ laser carried under varying laser processing parameters. The objective is to create a surface alloy with composition and microstructure, suitable for marine environments. The surface alloys were characterized using optical microscopy and scanning electron microscopy (SEM) and revealed the presence of the austenitic phase. Analysis by SEM-energy dispersive analysis (EDAX) revealed good compositional homogeneity with molybdenum contents in the range of 3 to 15 wt.%. The dendrite arm spacing (DAS) measured at the surface and bottom of the surface alloy using an image analyzer was found to be in good correlation with calculated cooling rates.