Anodic Profile Research Articles

Tool Design for ECM: Correction Factor Method

A simple model for tool (cathode) design for plane parallel electrochemical machining and electrochemical drilling has been proposed. Assuming the initial tool shape to be complementary to required work shape, the desirable and predicted anode profiles have been compared and the error between them has been evaluated. Using this error, the correction factor has been calculated to modify the tool shape. This procedure is repeated till the designed tool can produce an anode profile within the prescribed tolerance limits. Using this technique, tools for tapered, flat, exponential, parabolic, and nonstandard work shapes have been designed. Bare tools have been designed for straight and tapered sided holes. Comparison between analytical and experimental results shows a good agreement between them.

Prediction of anode profile in ECBD and ECDoperations

During electrochemical drilling, use of bit type of tools produce more accurate holes as compared to bare type of tools. But, no model is available to predict anode profiles obtained during electrochemical bit drilling (ECBD). In this paper, models SBFET-11 (one dimensional analysis) and SBFET-22 (two dimensional analysis), based on finite element technique, have been proposed. The models are capable to predict the workpiece shape and size obtained either by bit type of tool or bare type of tool. The models can analyse both types of workpieces, i.e. the workpiece having a predrilled hole and the workpiece without a predrilled hole. Some assumptions made in earlier models regarding zero void fraction, constant electrolyte flow velocity, zero feed rate in transition and side zones etc., have been relaxed. Special attention has been paid on the analysis of anode profile in the transition zone and its effects on the accuracy of the computed anode profile in side zone. Comparison of analytical and experimental anode profiles has revealed a good agreement between the two.

Investigations into the effect of cathode material on temperature distribution during electrochemical machining

SUMMARY Electrochemical machining (ECM) is one of the most widely used unconventional manufacturing processes. Its capabilities have not been fully exploited mainly because of some inherent problems associated with tool design. Most of the models available for tool design in ECM ignore the effect of the heat transferred through the cathode and anode and its effects on the variation of different process parameters during ECM. In the present paper, a simple thermal-resistance model of the ECM process is proposed. Using this model, the effects of the heat transferred through electrodes on temperature distribution, electrolyte conductivity, anode profile, metal removal rate (MRR), etc. have been studied. The experimental data have then been used to test the accuracy of the model. The tests show that, for accurate determination of the anode profile, any model which takes no account of the heat transferred through the electrodes will yield erroneous results.

MULTILAYER ANODIZATION PROFILE (MAP) A NOVEL DEPTH PROFILE TECHNIQUE FOR METALLIC–BASED LAYERED STRUCTURES

AbstractA simple and inexpensive technique is described, which makes novel use of electrolytic anodization to obtain an effective depth profile of artificial nultilayered structures based on a number of refractory metals. Successful MAPs (Multilayer Anodization Profiles) have been obtained for multilayer structures of Nb/Si, W/Ti, and a variety of other material pairs, with individual layer spacings ranging from less than 10 Å to greater than 50 Å. The spatial resolution of these MAPs annears to be less than about 10 Å, and may in some cases be comparable to the interface sharpness of the sputtered films. Comparison with conventional techniques such as Auger depth profiling and low–angle x-ray diffraction is discussed. Examples of semiquantitative analysis, using the MAP technique, of changes in interface structure brought about by thermal annealing, are also presented.

Some investigations into the anode profile in the transition zone in an electrochemical hole sinking operation

An empirical relationship has been suggested by some researchers to evaluate the overcut,ao, in the transition zone. But the detailed study of this relationship has revealed that it overestimates the value ofao for machining under large equilibrium gap conditions. In this paper, the authors give a simpler equation, based on regression analysis, for the estimation of overcut in the transition zone. Further,ao has also been found to be a function ofYe,f, D, rc andV.

Characterization of Carbon Steel Corrosion in Dilute Ammonium Nitrate Solutions and Irrigation Ground Waters

Abstract Ammonium nitrate fertilizer, distributed at concentrations of up to 0.1 w/o through irrigation systems, is a source of corrosion to structures, piping, valves, and electrical components. Corrosion behavior of synthetic mixtures and ground water samples was studied by potentiodynamic and linear polarization methods. Anodic profiles for low carbon steel in dilute mixtures of NH4NO3 and water are nonlinear and therefore not adaptable to direct Tafel analysis. Linear polarization correlates well with weight change and initial corrosion rates were found to vary between 12 to 20 mpy, depending upon NH4NO3 concentration. A combination of linear polarization and potentiodynamic scanning was used effectively to characterize corrosion in ground waters.

Silver-tin alloys and amalgams: electrochemical considerations.

The corrosion potential and anodic polarization profiles of a representative number of silver-tin alloys and their corresponding amalgams in a physiological solution were determined and compared to their microstructures. For the alloys with tin-content greater than 27%(wt) and for all amalgams, the corrosion process is related to the attack of free tin for the alloys and to the gamma-2 tin for the amalgams. The gamma-2 concentration in the amalgams increases with an increase in tin-content. For alloys with tin-content less than 27%, the corrosion process is even more restricted than for the process observed with pure silver. From a developed theory based upon the potential-time and polarization results, association of the O2 reduction process on a SnO cathodic film to an intermediate specie of H2O2 is made. The rate of H2O2 decomposition on a SnO surface in a four electron process is thought to control the O2 reduction overvoltage. The O2 reduction overvoltage decreases with increases in the silver-content of the amalgam, particularily seen with the 8 and 12% tin compositions. Due to the polarization induced corrosion process, a phase with high silver and high mercury concentrations was observed over the unreacted particles.

Anodic Oxidation and Electrical Carrier Concentration Profiles of Ion‐Implanted InP

A technique is described that combines controlled anodic oxidation with differential Hall data to obtain electrical carrier concentration profiles of ion‐implanted indium phosphide. Reproducible oxide layers are grown using a citric acid, ethylene glycol electrolyte bath and a controlled voltage rise technique. A variation in material consumption with anodic oxide thickness and with anodizing technique is observed. For the purposes of demonstration, silicon and sulfur species implanted at 1 MeV to fluences of are examined. These profiles are measured on <100> implanted semi‐insulating. The technique could be adapted to measure other alloys in the system.

In vitro polarization of dental amalgam in human saliva

Potentiostatic anodic polarization techniques in Ringer's solution are commonly used for the evaluation of the corrosion resistance of dental amalgam. This in vitro method strives to simulate the in vivo electrochemical behaviour of amalgam in an electrolyte of natural saliva. Several types of dental amalgam were anodically polarized in natural saliva solutions and supernatant saliva solutions. The anodic polarization profiles are presented, as well as scanning electron micrographs and x-ray analysis of the corroded amalgam surfaces. These reveal corrosion products consistent with results found with previous artificial salivas as well as deposits possibly related to the organic component of natural saliva.

Electrochemical properties of copper and gold containing dental amalgams.

Alloying or admixing of a dental amalgam alloy with an element or alloy which has a higher affinity for tin offers a means for eliminating the corrosion prone gamma2 phase. Accordingly, the corrosion behaviour of non-conventional amalgams containing Cu and Au were investigated by anodic polarization studies in Ringer's solution. The Cu containing amalgams were produced by admixing Cu-Hg (copper amalgam) with conventional amalgam in the ratios of 0-5:1 and 1:1. A 10 w/o Au in Ag-3-Sn was used as the gold amalgam alloy. The anodic polarization profile of the 0-5:1 Cu admixed was similar in shape to admixed conventional amalgams although current densities were less. After ageing for 1 month the minus 250 mV peak associated with gamma2 disappeared and the current density decreased by ten fold. After 2 months the current density decreased by one hundred fold. The anodic polarization of the 1:1 Cu admixed amalgams did not display the minus 250 mV (gamma2) peak after 1 week and current densities were 10-3 below that of conventional amalgams. The behaviour of these interesting amalgams is rationalized on the basis of the ease of formation of Cu-Sn intermetallics where Cu/Sn larger than or equal to 3. The anodic polarization profile of 10 w/o Au containing amalgam essentially is that of conventional amalgam and does not change drastically after 6 months. Although the Au may reduce or eliminate the gamma2 phase the resulting AuSn4 apparently corrodes in an analogous fashion. However, since distribution of AuSn4 may be different from gamma2, i.e. not continuous, the effect of corrosion on its mechanical properties may be different.

Electrochemistry of the saline corrosion of conventional dental amalgams.

The electrochemical behaviour of the component phases of dental amalgam, viz. Ag3Sn(gamma),Ag2Hg3(gamma1), Sn7-8Hg(gamma2),Cu3Sn, Cu6Sn5 and a composite of gamma1 + gamma2 phases were evaluated in saline solution by standard anodic polarization techniques. Using multi-electrode theory a theoretical polarization diagram was constructed from the composite phases and compared with an anodic polarization profile attained from conventional dental amalgam. A strong agreement was obtained. From analysis of the electrochemical reactions it was found that the passivity of gamma2 is due to the formation of stannous and/or stannic oxide (hydroxide) and that the corrosion failure of dental amalgam occurs through the dissolution of this passive oxide in gamma2 at potentials of minus 250 mV Vs. SCE with the formation of tine oxychloride. The corrosion behaviour of Cu6Sn5 is similar to that of gamma2 phase and its presence impairs the corrosion resistance of dental amalgam. If the copper containing phase is Cu3Sn, it will be passive in Ringer's solution, possibly as a result of Tamman's "multiple rule of eight".

Mechanism of the electrooxidation of ethyl alcohol and acetaldehyde on a smooth platinum electrode: III. Potential sweep investigation with varying reversal potential

Anodic and cathodic current-potential profiles in sulphuric acid solutions of ethylalcohol and acetaldehyde on smooth Pt electrode recorded under potential sweep conditions with varying reversal potential are discussed. The experimental results are in accordance with the concepts given earlier about the mechanism of the electrooxidation of the examined organic substances in the double layer and oxygen potential range. The distinction in the electrochemical behaviour of ethyl alcohol and acetaldehyde is related to the smaller part of the destructive chemisorption of the aldehyde in the overall anodic process. No dependence of the mechanism on the roughness factor is observed.

Grain-boundary solute electromigration in polycrystalline films

It is demonstrated that with proper analysis of the diffusion profiles, the effective charge and diffusivity for grain-boundary electromigration can be separately measured. Electromigration profiles are analyzed based on Fisher-type approximations for an equiaxial and perfectly textured grain structure. Electromigration profiles were obtained for Cu in Al at 255°C by measuring the spreading of a Cu cross-stripe subject to a direct current; the results were checked by annealing experiments performed under similar conditions. Cu was observed to migrate in the direction of electron flow. Results obtained from analysis of the anode and annealing profiles are −16.8±1.2 for the effective charge and (1.75±0.12) × 10−14 cm3/sec for the diffusivity parameter αDbδ. The over-all consistency of the results is better than 5%. Whipple analysis gives a more exact value of (2.74±0.16) × 10−14 cm3/sec for αDbδ.

Scanning Electron Microscopy of Contact Surfaces Before and After Arcing

An apparatus has been constructed which allows the manipulation of electrical contacts inside a scanning electron microscope. The contact members can be positioned so that an image of their edge profiles can be obtained at magnifications as high as 10,000X. The microgeometry of both the anode and cathode surfaces is clearly imaged. The contacts can be brought together to make electrical contact and then separated to a desired distance. The interelectrode spacing and both contact members can be viewed on the cathode ray tube of the scanning electron microscope. With this technique, contact gaps of less than one micron can be set and measured. Both contacts are connected to coaxial cable circuitry external to the microscope. A pulse of predetermined potential and duration can be transmitted to one of the contact members. If breakdown occurs, an oscillographic record of the event is obtained as well as an immediate image of the damage on the anode and cathode profiles. One of the contacts can then be rotated to obtain a front view for measurements of the arc damage. Using this technique the phenomenon of electrode bridging from an eruption of molten metal from the anode has been observed. Electric fields required for the initiation cf short arcs have been measured as have the diameters of anode craters and their rim heights

Study of the anodic profile in an electrolyser with rotating soluble anode floating on a flat inert cathode

The present investigation deals with the conditions of fluidodynamical and electrochemical equilibrium which develops in thinning metal disks in an electrolyser supplied with a flat inert cathode on which floats a rotating anode. These working conditions are characteristic of a new technique for the electrochemical thinning of metallic foils. The analytically simpler case of absence of rotation was considered first. Then the more complex case, in which the anode also participates in this movement, was examined. The two cases lead to film thickness profiles which are practically identical, at least as regards rotation speeds between zero and 300 rev min-1. The experimental data obtained in thinning tests on specimens of commercial steels previously subjected to thermic treatment of technological interest, and using as electrolyte solutions of HNO3 in low concentration were in good agreement with theoretical values. In particular we have seen that at the circular external rim of the specimen, where the equilibrium profile deviates in least degree from flatness, such a deviation is less than 20/00. A quantitative verification of the hypotheses on which this theoretical study was based has shown the validity of these hypotheses in the running conditions examined.