Polishing, electrolytic

In contrast chemical and electrolytic polishing enables a smooth level surface to be produced without any residual stress being developed in the surface because the surface is removed by dissolution at relatively low chemical potential and at relatively low rates is such a way that metallic surface asperities are preferentially removed. For this to be most effective the solution properties must be optimised and the pretreatment must leave an essentially bare metal surface for attack by the electrolyte. 

Lead sulfide films have been prepared by various deposition processes like vacuum evaporation and chemical bath deposition. Electrochemical preparation techniques have been used in a few instances. Pourbaix diagrams for all three aqueous lead-chalcogen Pb-S, Pb-Se, and Pb-Te systems, along with experimental results and cited discussion on the chemical etching and electrolytic polishing of lead chalcogenide crystals and films, have been presented by Robozerov et al. [201]. 

Preparation A significant number of papers, which have appeared over the last decade, are focused on the studies of the Ag(bkl) surface in contact with various species. Our concise survey covers only those that are most relevant to electrochemists. In the electrochemical practice, the most intensively studied Ag surfaces include Ag(lll), Ag(lOO), Ag(llO), and Ag(OOl), whereas the number of papers devoted to, for example, Ag(210) and Ag(410) is substantially smaller. Electrode surfaces can be prepared in various ways electrolytic growth in a Teflon capillary, electrolytic polishing of Ag single crystals, or chemical (Gr03 + H2O) polishing of Ag crystal... 

Experimentally, work-function measurements which rely on the cold emission of electrons are carried out in the field-emission microscope (F.E.M.) (21). The apparatus, as shown in Fig. 11, consists of a W tip P sharpened by electrolytic polishing so that the radius of curvature is 10 cm., and an anode in the form of a film of Aquadag. A variable potential of 3 to 15 kv. is applied to the anode, and the electrons, pulled out from the point, travel in approximately straight lines to the fluorescent screen. The linear magnification obtained is of the order of 10 to 10. The secondary electrons from the screen are collected by the anode, and the field-emission current is measured by a sensitive microammeter. 

The safe use of AcaO—HClO as electrolytic polishing bath has been investigated by Hikita Asaba (Ref 12) and by Me dard Sartorius (Ref 10) resulting in a 3 phase diagram to show the dangerous zones... 

O Neil (1967) analysed the influence of alloy admixtures in small amounts, e g-, 5% copper, in very hard a-manganese on the softening of the solid solution in order to raise its compliance to electrolytic polishing. 

About this time electrolytic polishing was developed by Jacquet (13), and, when it was applied to a single crystal, it was possible to obtain a highly polished surface on all faces at the same time. Through the use of the crystal in the form of a sphere, a specimen could be obtained which ex-... 

In this method of study there are two important steps in the preparation of the specimen. The first is the growth of the single crystal itself, and the second is the preparation of the surface. Large single crystals of metals have been used for about fifty years largely for the study of physical and mechanical properties of metals, and it is only recently with the advent of electrolytic polishing that it has been possible to use them for the study of reactions between metals and gases. 

Electrolytic-grade nickel (99.98 mass % Ni) was used in the form of polished plates 3x9x14 mm3. Their final treatment involved electrolytic polishing, both to remove the surface contaminations and to reduce mechanical stresses. 

The Ni-Bi couples were annealed in sealed glass ampoules, filled with high-purity helium (0.25 atm), at 150, 200 and 250°C for 1 to 300 h. Each couple was annealed successively a few times. After each anneal, the specimen surface was examined in the as-received conditions and after mechanical and/or electrolytic polishing. 

Fig. 1.16. Secondary electron image of the Ni-Bi transition zone and the concentration profiles of both components within the phases involved in the interaction.149 Temperature 250°C, annealing time 9xl04 s (25 h). Electrolytic polishing.

Electrolytic polishing, discovered by Jacquet in 1935, has the distinct advantage of completely eliminating the structural surface damage caused by classical mechanical polishing. 

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