Electrochemical Surface Finishing Research Articles

(Invited) Case Studies for in-Space Electrochemical Operations

Faraday Technology Inc. is a research, development and electrochemical engineering firm developing electrochemical innovations for terrestrial and space system.[1,2] With that founding basis Faraday has been able to bridge the gap between academic understanding and small-scale demonstrations to commercialization of practical components for over 32 years of operation.This presentation will discuss a broad range of electrochemical approaches to improve the performance of components used in space or to be used for in-space production. We will provide insight into case studies, performed at Faraday, from our four business units of electrodeposition, electrochemical surface finishing, electrochemical conversion, and electrochemical system design. For instances, we will discuss direct print electrodeposition, electrophoretic application of coatings for glare resistance, surface finishing of rocket components, bioelectrochemical treatment of urine, and the generation of peroxide. Each electrochemical process has applications on earth and in space; additionally, each program had to overcome specific challenges that only space can present.

SURFACE QUALITY AND CORROSION RESISTANCE OF 316L STAINLESS STEEL ELECTROPOLISHED USING PHOSPHORIC – SULFURIC ACIDS

Electropolishing is an electrochemical surface finishing technique. It is commonly applied to equipment that requires a gleaming finish. This surface property is frequently required in 316L stainless steel (SS) medical implants. Electropolishing removes a thin layer from the metal's surface through electrochemical processes. This results in a very clean, smooth, and bright metal surface. The process parameters, such as electrolyte solution, electrical current, and electropolishing time, influence surface roughness and glossiness. The dissolution of metallic ions during the process may also affect the corrosion resistance of the treated material in addition to producing a shiny surface. This study investigated the surface glossiness, surface roughness, and corrosion of electropolished 316L SS. Electropolishing experiments on 316 SS were carried out using various H3PO4 (50%) and H2SO4 (32%) electrolyte solution compositions. The influences of electrolyte solution composition, electric current, and electropolishing time were studied. The results showed that increasing the H2SO4 content of the mixture and electropolishing the 316L SS for a longer period of time improved the surface roughness and glossiness. Under 10 Amp electric currents, the best surface glossiness was discovered. A corrosion test revealed that the electropolishing produced a Cr and Ni-rich layer that improved the corrosion resistance of the samples.

Electrodissolution Processes and Their Application in Manufacturing for Shaping and Finishing of Advanced Materials

Controlled material removal by anodic dissolution at high rates forms the basis of non-conventional metal shaping and finishing processes such as Electrochemical Machining (ECM), Electrochemical Micromachining (EMM), and Electropolishing (EP). These processes are employed in the manufacturing and processing industries for a variety of applications ranging from the machining of complex shaped components for heavy industries to the fabrication of microstructures in thin films and foils and microfinishing of superconducting radiofrequency cavities (1-3). Application of these processes for the production of reliable, reproducible, and high-yielding components require an understanding of the parameters that influence the anodic dissolution processes.ECM, EMM, and EP can be understood and theoretically modeled based on the same principles provided the scaling effects related to each process are considered (2). In the first part of this presentation, the high rate anodic dissolution behavior of different materials including refractory materials are described which helps in establishing the basic concepts that govern ECM/EMM/EP processes. Electrochemical reactions taking place at high anodic potentials depend on the metal-electrolyte combination and the operating conditions. These reactions include active metal dissolution, passivity, oxygen evolution, and the phenomena of passive film breakdown leading to the transpassive metal dissolution. In passivating electrolytes (containing oxidizing anions), oxygen evolution and metal dissolution take place simultaneously. The current density dependence of meat dissolution efficiency in such electrolytes provides minimized stray cutting in ECM. Mass-transport, current distribution, and surface film properties play a significant role in the metal removal rate and surface finish. Whereas the formation of a salt film on the dissolving anode in ECM electrolytes is well established, the identification of the rate-controlling species during electropolishing of metals in concentrated acid solutions remains a controversial issue.The second part of the presentation deals with the applications of these processes in the manufacturing of advanced products for the aerospace, biomedical, electronics, and photovoltaics industries. Different ECM techniques such as die-sinking, combined tool machining, EC drilling, and EC deburring are described that are used in the manufacturing of complicated shaped parts such as turbine blades. Maskless EMM methods such as Jet EMM, micro-drilling, and wire EMM are applied to fabricate precision microstructures. For process enhancement, assisted techniques such as laser, abrasive, vibration, and ultrasonic are incorporated with maskless EMM. For through mask electrochemical micromachining (TMEMM), an understanding of mass transport in a cavity and shape evolution modeling is critical. The use of laser patterned oxide film mask for Ti patterning is presented as an interesting application of TMEMM (4). A few case-studies on electropolishing are described which include the fabrication of STM probes and Nitinol stents, and microfinishing of print bands. In the microprocessor industry, a significant effort was invested in the development of EP and electrochemical mechanical planarization (ECMP) approaches as a no-contact or low-contact planarization processes for the integration of ULK/copper interconnects. The development work, including processing details and planarization efficiency of EP and ECMP, are reviewed. A critical evaluation of the current status of EP/ECMP vis a vis the chemical mechanical planarization (CMP) process is presented.References J. McGeough, Principles of Electrochemical Machining, Chapman and Hall, Wiley, London, 1974.M. Datta, Electrodissolution Processes: Fundamentals and Applications, CRC Press/Taylor and Francis, Boca Raton, 2020.E. J. Taylor and M. Inman, Electrochemical Surface Finishing, The Electrochemical Society Interface, Fall 2014, p47.P.-F. Chauvy, P. Hoffmann, D. Landolt, Electrochemical Micromachining of Titanium Through a Laser Patterned Oxide Film, Electrochem. Solid-State Lett., 4(5), C31 (2001).

Electrodeposition of Al-Cr-Mn Alloys from Chloroaluminate Ionic Liquids

Despite the emergence of many new ionic liquid systems or room-temperature molten salts, chloroaluminate ionic liquids are still one of the most versatile systems for the electrochemical surface finishing of metals. The most commonly studied chloroaluminate IL is the well-known mixture of AlCl3 and the quaternary ammonium chloride salt, 1-ethyl-3-methylimidazolium chloride (EtMeImCl).1 Among the anhydrous, aprotic ILs prepared to date, this mixture still holds the record for the highest conductivity and lowest viscosity. Save for the need to protect it from exposure to moisture, it is undoubtedly one of the most versatile IL systems for electrochemistry. In most cases, the acidic composition of this IL proves to be the most valuable composition for surface finishing, owing to the presence of the coordinately unsaturated Lewis acidic species, Al2Cl7 -, which is readily reduced to Al metal via the reaction:4Al2Cl7 - + 3e- ⇌ Al + 7AlCl4 - (1)The electroplating of Al from chloroaluminate ILs, such as AlCl3-EtMeImCl, is one of the most thoroughly studied processes in the field of ionic liquid electrochemistry, as attested in a recent review.2 However, much less attention has been devoted to the electrodeposition of aluminum alloys from these ILs, many of which have very useful properties. Stable alloys can be obtained during the electrodeposition of Al if certain low valent transition metal ions, M z +, that are reduced negative of the potential required for the reaction shown in Eq. 1 are added to the acidic IL, e.g., Cr2+, Ti2+, V2+, Mo2+, and Mn2+, to name a few.2 In this case, it is possible to prepare aluminum-transition metal alloys: xM(AlCl4) p (p-z)- + 4(1-x)Al2Cl7 - + [3-(3-z)x]e- ⇌ M x Al1-x + [7(1-x) +px]AlCl4 - (2)where x represents the fraction of the transition metal in the M x Al1-x alloy. For some values of x, these so-called “overpotential alloys” form single-phase metallic glasses. In this case, these amorphous, non-equilibrium alloys exhibit a greatly enhanced resistance to chloride pitting corrosion relative to pure Al. Ternary alloys with metallic glass phases can also be produced by adding a second transition metal to the acidic IL. Articles have appeared in The Journal describing the electrodeposition and properties of such aluminum alloys containing Mn + Mo,3 Mo + Ti,4 and Mn + W.5 In general, coatings prepared with ternary alloys display enhanced resistance to chloride pitting corrosion compared to the corresponding binary alloys. In this poster, we describe recent work on the electrodeposition of Al-Cr-Mn ternary alloys.

Anodic Dissolution of Copper in the Aluminum Chloride-1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid

The ever popular AlCl3-1-ethyl-3-ethylimidazolium chloride (EtMeImCl) ionic liquid (IL) system offers a unique solvation environment for many metal ions. In fact, the use of these chloroaluminate ionic liquids for the electrochemical surface finishing of metals was recently reviewed.1 These ionic liquids display adjustable Lewis acidity that depends directly on the mole ratio of the AlCl3 to the organic salt. The basic AlCl3-EtMeImCl mixture, which contains coordinately unsaturated Cl-, provides a solvation environment similar to aqueous HCl and NaCl, except of course without the complications due to the H2O solvent or H3O+. The opposite situation prevails in the Lewis acidic ionic liquid because the main chemically active ionic component of the ionic liquid is the coordinately unsaturated species, [Al2Cl7]-. Thus, there are no “hard” ligands available to form stable, isolable anionic complexes with the anodization product. Recently, both composition regions of the AlCl3-EtMeImCl IL system have been explored for the electrodissolution/electropolishing of Al.2 The advantages afforded by anodic dissolution of metals in this ionic liquid relative the aqueous acids and salt solutions commonly used for this purpose are quite obvious, i.e., the avoidance of the oxide surface films that invariably complicate the metal electropolishing process. In this paper, we report the thermodynamics and kinetics of the anodic dissolution of copper metal in the acidic and basic compositions of the AlCl3-EtMeImCl ionic liquid. In the former, the dissolution of copper at a Cu-RDE exhibits mixed control. No limiting current or passivation due to the formation of an insoluble surface film was apparent. In the basic composition region, mixed control was observed at small overpotentials, but as the overpotential was increased, a limiting current was obtained that scaled linearly with the Cl- concentration in the ionic liquid. The connection between these results and the mechanism of the dissolution process will be discussed.____________________________________________ 1. T. Tsuda, G. R. Stafford and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017).2. C. Wang and C. L. Hussey, J. Electrochem. Soc., 163, H1186 (2015).

(Invited) Surface Finishing with Chloroaluminate Ionic Liquids

Despite the emergence of many new ionic liquid systems or room-temperature molten salts, chloroaluminate ionic liquids are still one of the most versatile systems for the electrochemical surface finishing of metals, whether it be the electrodeposition of corrosion protective films on steel or the electrochemical polishing of metal surfaces, such as Cu. The most commonly studied chloroaluminate IL is the well-known mixture of AlCl3 and the quaternary ammonium chloride salt, 1-ethyl-3-methylimidazolium chloride (EtMeImCl).1 Among the anhydrous, aprotic ILs prepared to date, this mixture still holds the record for the highest conductivity and lowest viscosity. Save for the need to protect it from exposure to moisture, it is undoubtedly one of the most versatile IL systems for electrochemistry. In most cases, the acidic composition of this IL proves to be the most valuable composition for surface finishing, owing to the presence of the coordinately unsaturated Lewis acidic species, Al2Cl7 -, which is readily reduced to Al metal via the reaction: 4Al2Cl7 -+3e- ⇌Al + 7AlCl4 - (1) The electroplating of Al from chloroaluminate ILs, such as AlCl3-EtMeImCl, is one of the most thoroughly studied processes in the field of ionic liquid electrochemistry, as attested in a recent review.2 However, much less attention has been devoted to the electrodeposition of aluminum alloys from these ILs, many of which have very useful properties. Stable alloys can be obtained during the electrodeposition of Al if certain low valent transition metal ions, Mz+, that are reduced negative of the potential required for the reaction shown in eq 1 are added to the acidic IL, e.g., Ti2+, V2+, Mo2+, and Mn2+, to name a few.2 In this case, it is possible to prepare aluminum-transition metal alloys: xM(AlCl4) p (p-z)- + 4(1-x)Al2Cl7 - + [3-(3-z)x]e- ⇌M x Al1-x + [7(1-x) +px]AlCl4 - (2) where x represents the fraction of the transition metal in the M x Al1-x alloy. For some values of x, these so-called “overpotential alloys” form single-phase metallic glasses. In this case, these amorphous, non-equilibrium alloys exhibit a greatly enhanced resistance to chloride pitting corrosion relative to pure Al. Ternary alloys with metallic glass phases can also be produced by adding a second transition metal to the acidic IL. Articles have appeared in The Journal describing the electrodeposition and properties of such aluminum alloys containing Mo + M, Mo + Ti, and W + Mn. Recently, both the Lewis acidic and basic composition of the AlCl3-EtMeImCl IL system have been explored for the reverse purpose, the electropolishing of Al and Cu by anodic dissolution. The advantages afforded by anodic dissolution in these ILs relative the aqueous acids and salt solutions commonly used for this purpose are quite obvious, i.e., the avoidance of the oxide surface films that invariably complicate the electropolishing process. In this paper, we report recent advances in the electrodeposition of aluminum transition metal alloys for metal surface finishing as well as the thermodynamics and kinetics of the anodic dissolution of metals in the acidic and basic compositions of the AlCl3-EtMeImCl IL system.

Electrochemical Surface Finishing of Additively Manufactured Parts

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

Electrochemical Surface Finishing of Additively Manufactured Parts

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

Electrochemical Surface Finishing of Additively Manufactured Parts

This paper will discuss our progress in developing surface finishing techniques for additively manufactured aerospace alloys. Additive manufacturing (AM) processes have the potential to revolutionize the art of manufacturing complex components, essentially enabling a build to print scenario where the designer has unlimited bounds. However, when printing fine featured metallic materials using powder bed (pb) approaches the surface left by the AM process are usually rough with adherent particles (20 to 75 µm in diameter) covering the entirety of the surface. In the following paper we will discuss our electrochemical finishing approach to eliminate these surface defects and finish the surface with as little material removal as possible. Furthermore, we will discuss our approach to finishing of grade 5 titanium alloy (Ti64) produced via an electron beam pb-AM approach and using various electrolytes and both as built and post hot isostatically pressed (HIPped) components.

Electropolishing effect on roughness metrics of ground stainless steel: a length scale study

Electropolishing is a widely-used electrochemical surface finishing process for metals. The electropolishing of stainless steel has vast commercial application, such as improving corrosion resistance, improving cleanness, and brightening. The surface topography characterization is performed using several techniques with different lateral resolutions and length scales, from atomic force microscopy in the nano-scale (<0.1 µm) to stylus and optical profilometry in the micro- and mesoscales (0.1 µm–1 mm). This paper presents an experimental length scale study of the surface texture of ground stainless steel followed by an electropolishing process in the micro and meso lateral scales. Both stylus and optical profilometers are used, and multiple cut-off lengths of the standard Gaussian filter are adopted. While the commonly used roughness amplitude parameters (Ra, Rq and Rz) fail to characterize electropolished textures, the root mean square slope (RΔq) is found to better describe the electropolished surfaces and to be insensitive to scale.

(Invited) Pulsed Current Deposition: From Nano-Crystalline to Multi-Functional Coatings

The electrochemical deposition of metals and alloys using alternating uni- and bipolar current profiles, in short Pulse Plating technologies, has found the interest of both researchers and companies worldwide in recent years. The use of a modulated current deposition opens a wide field of new possibilities in electrochemical surface finishing as has been discussed at many occasions such as the biannual international conference “European Pulse Plating Seminar” and the Interfinish 2012. While the starting point often has been the aim for nano-crystallinity of deposited coatings, being still one major advantage of pulse plating in the technical awareness of the users, there are nowadays different approaches enabling a combined functionality beyond the nano-crystallinity. Any pulsed electrodeposition process should be based on a fundamental knowledge of the deposition mechanisms and thus requires for the initial set up a profound study of electro kinetics, mass transport limitations and electro-crystallization effects. Electrochemical measurements at laboratory scale and structural analysis of the electrodeposits in dependence on the plating parameters applied will enable the definition of suitable pulse plating sequences. This presentation will discuss the possibilities and applications of generating multi functional layer systems based on the concept of depositing nano-crystalline layers via pulse plating techniques. The electrochemical parameters and concepts for achieving nano-crystalline layers will be explained supported by electrochemical fundamentals. Advantages and limitations of such nano-crystalline coatings will be briefly discussed. Using the results of several (international) fundamental and applied research projects, funded by the European Union strategic research programs, more sophisticated benefits of pulse plated metal alloy coatings will be presented. This will include the incorporation of nano-particles in the metal coating (nano-dispersion coatings), alloy deposition and surface property adjustment. Beside electrochemical experiments for gaining a profound knowledge of the electrolyte properties and the reaction mechanisms, the only way to quantify field line distribution and potential fields, even in a local resolution, are numerical simulation tools. Based on the characteristic electrode kinetics, possible resistive effects at the electrode surface, the general plating conditions (e.g., electrolyte temperature) and the electrolyte properties (e.g., conductivity) a numerical simulation software tool has been used, allowing the exact calculation of current field line distribution and potential fields between two electrodes. Pulse plating with its numerous possibilities to control electrochemical conditions directly at the (substrate) surface, will allow to precisely control the alloy composition of deposited binary and ternary alloys just by adjustment of the pulse parameters. Thermal, electrical properties as well as magnetic properties of the resulting coatings can be adjusted by this method. The underlying nano-crystallinity will additionally increase the resulting layer hardness. The incorporation of particles to form a (nano) dispersion coating will provide hardness and wear resistance better and more stable than pure nano-crystalline coatings. This presentation will be complemented by several examples of the industrial use of pulse plating for high-tech components and mass production parts.

Electrochemical Surface Finishing of Additively Manufactured Parts

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

Looking at Patent Law: Patentable Inventions, Conditions for Receiving a Patent, and Claims

This installment of the semi-regular column on patent law looks at what can constitute a patentable invention and what are the conditions for receiving a patent or claim. From an electrochemical perspective there are five statutory classes of patentable inventions such as a process or method for an electrodeposition, electrochemical surface finishing or electrosynthesis process; a machine or apparatus such as an electrolytic cell; a manufacture or product using an electrochemical process; a composition of matter or chemical compound or alloy such as a battery electrode material; or an improvement of said process, machine, manufacture, or composition of matter. Attention is given to the definition of a person having ordinary skill in the art (PHOSITA). 32 references.

Review—Electrochemical Surface Finishing and Energy Storage Technology with Room-Temperature Haloaluminate Ionic Liquids and Mixtures

In this article, we review the progress in the area of electrochemical technology with Lewis acidic haloaluminate room-temperature ionic liquids (RTILs), such as AlCl3–1-ethyl-3-methylimidazolium chloride and AlBr3–1-ethyl-3-methylimidazolium bromide, and novel chloroaluminate mixtures consisting of AlCl3 and polarizable molecules, e.g., dimethylsulfone and urea, during this decade. The number of researchers in the field seems to increase steadily, because now we can handle haloaluminate RTILs and their mixtures with other solvents and materials more easily than we could in the past. In this review, we have categorized the electrochemical technology based on these RTILs into two topics: electroplating and energy storage. In fact, much of the current research is based on work begun during the period from ∼1970 until the 1990’s. But new findings and insights have been obtained through the application of state-of-the-art technologies. With this new information, haloaluminate RTILs and solvent mixtures have the spotlight again.

Electrochemical Surface Finishing

Electrochemical surface finishing is a highly scalable manufacturing process that traditionally uses viscous, non-aqueous and/or highly acidic electrolytes to achieve the desired surface profiles on metallic parts, with the addition of aggressive, hazardous chemical species to remove the oxide film on strongly passive materials. An emerging approach applies pulse and pulse reverse electric fields to control current distribution, mitigate oxide film formation and achieve the desired surface finish, in the presence of environmentally benign and simple chemistries. This approach lowers the cost of the manufacturing process, and improves process robustness. After a brief discussion of electrochemical surface finishing processes, case studies that describe deburring of automotive gears and electropolishing of semiconductor valves and superconducting radio frequency cavities are presented in this article. Conventional Electrochemical Surface Finishing Processes Electrochemical surface finishing removes metal in a selective manner from the surface of the workpiece by converting the metal into ions by means of an applied electric field. This is accomplished in an electrolytic cell by applying a positive (anodic) potential to the workpiece and a negative (cathode) potential to the tool used to shape the workpiece. While fundamental investigations of electrochemical metal removal processes typically employ a 3-electrode system, a manufacturing environment is typically not conducive to the use of reference electrodes. Therefore, most electrochemical manufacturing systems are based on a two-electrode cell. Conventional electrochemical surface finishing relies heavily on the “art” of chemical mediation for process control. Under the influence of a constant electric field and controlled electrolyte flow, aggressive chemical species diffuse to the electrochemical interface and control the preferential dissolution of asperities from a surface via an electrolytic reaction, which may be generally represented as:

Electropolishing of Passive Materials in HF-Free Low Viscosity Aqueous Electrolytes

A pulse reverse electrochemical surface finishing process for electropolishing passive materials is described. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes and does not require the addition of chemical species to remove the passive film associated with electropolishing of passive and strongly passive materials. This paper focuses on pulse/pulse reverse electropolishing of niobium and Nitinol.

Electropolishing of Passive Materials in HF-Free Low Viscosity Aqueous Electrolytes

A pulse reverse electrochemical surface finishing process for electropolishing passive materials is described. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes and does not require the addition of chemical species to remove the passive film associated with electropolishing of passive and strongly passive materials. This paper focuses on pulse/pulse reverse electropolishing of niobium.

Surface Finishing of High Speed Print Bands: I. A Prototype Tool for Electrochemical Microfinishing and Character Rounding of Print Bands

A prototype tool is described for electrochemical surface finishing of an anodic workpiece in strip form, such as the stainless steel print bands used in high speed printers. The tool consists of two units, an electropolishing unit for microfinishing of print bands, and a directional electroetching assembly to provide rounding of characters in the print band. The prototype tool is completely automated and has provisions for rinsing and drying of the mounted print band. Buffed and unbuffed print band samples were used for process development and feasibility testing of the tool. Results demonstrated that the described electrolytic process yields reproducible mirror‐finished print band surfaces with desired leading and trailing edges of characters. The process is applicable either as a complement to traditional buffing to give a final microfinish to print bands, or it can replace the presently used buffing technique for character rounding and surface finishing.

ChemInform Abstract: HIGH RATE TRANSPASSIVE DISSOLUTION OF NICKEL WITH PULSATING CURRENT

AbstractDie Stromausb.

High rate transpassive dissolution of nickel with pulsating current

The influence of pulsating current on high rate transpassive dissolution of nickel in 6 M NaNO 3 has been investigated. Obtained results indicate that current efficiency for nickel dissolution is influenced by pulse time and to a certain extent by relaxation time and is related to the anion build up at the anode. Dissolution efficiency for a given average current density is higher under pulsating current than direct current conditions. The influence of different pulse parameters on the anode potential and on the onset of sparking are investigated. The use of a pulsating current provides additional possibilities to influence the transpassive dissolution behavior in electrochemical machining and surface finishing operations.