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A so-called blockage geometry consisting of a rod with a fin positioned concentrically within a pipe is used to asses the capabilities of numerical turbulent flow and mass transfer models to predict the turbulent mass transfer coefficients. Measurements of the mass transfer coefficient have been performed for a range of fin diameters and flow rates. The limiting diffusion current measurements were performed using the ferri-ferrocyanide system and nickel electrodes. Different mass transfer turbulence models are used for the calculations and the results are compared with the measurements. The influence of flow rate and fin diameter on the mass transfer rate is examined.

A new two-dimensional model is presented that allows describing the high speed electrochemical machining of steel in NaNO3 solutions. Unlike existing models, local ion concentrations are calculated and used to evaluate local diffusion coefficients and electrolyte conductivity. Secondly, the presence of a super-saturated, honey-like layer on the anode surface is accounted for by introducing a water depletion factor. This factor describes the suppression of the oxygen evolution as the vast increase in ion concentrations reduces the amount of free water molecules at the anode. It is demonstrated that this approach enables to reproduce experimental average efficiency curves over a broad range of electrolyte concentrations with just a limited set of adjustable parameters.

Laminar and turbulent mass transfer in a parallel plate reactor at high Schmidt number obtained from numerical simulation is compared with literature data. In a first step, the fluid flow is determined numerically in the reactor by solving the Navier–Stokes equations. For turbulent flow, a low Reynolds number k—ω model is used to calculate the turbulent viscosity. Using the obtained flow field and turbulent viscosity, the current density distribution is calculated for different flow velocities by solving the equations describing the transport of multiple ions due to diffusion, convection and migration. For the laminar case, a very good agreement with literature data is obtained. For turbulent flow, different numerical models for turbulent mass transfer are proposed in the literature. A detailed study of the behaviour close to the wall of these different turbulence models is presented, together with a comparison of the calculated results with literature correlations. This allows identification of the benefits and disadvantages of each of the turbulence models for the numerical calculation of mass transfer at high Schmidt numbers in a parallel plate reactor.

Formed and welded metal PEM fuel cell bipolar plates are the most prominent strategy to reach low cost and high performance in a high volume production environment. Using the proprietary coil-based Hydrogate proces, Borit is able to achieve world class thin sheet metal forming with excellent repeatability and reproducibility. An overview of the typical process flow for metal bipolar plate production, process capabilities and yields will be shown. Implementing the appropriate process controls overcomes the challenges related to laser welding of thin metal foils with constraints regarding plate flatness, leak tightness and weld strength. An update on the latest developments will be presented, together with the related QC and traceability efforts.

The influence of heat transfer on anodic oxide growth during anodizing of high purity Al is studied on a laboratory scale in a wall-jet electrode reactor under different flow conditions. Local electrode temperatures are monitored by temperature measurements on the backside of the anode, whereas the effect of local temperature on film growth is evaluated by FE-SEM analyses. Quantitative information on the conditions of heat transfer is provided by numerical calculations of the flow field, and is applied during simulations of the anodizing process. The impact of the flow field, calculated by two different turbulence models, on the simulations is verified.

The current and copper deposit distribution on a metallic fibre (stainless steel, diameter of 2 mm) was studied numerically and experimentally. The experimental copper deposit was measured with an optical microscope and the current distribution was deduced. The influence of electrolysis time on copper deposit distribution was also studied. A typical current tertiary distribution was observed. The experiment with a longer electrolysis time exhibited a larger current variation around the wire. A numerical study of this problem was also carried out. The simulation involved a laminar and turbulent flow solver together with a numerical model for the mass transfer of ionic species due to diffusion, migration and convection. A good correlation was found between simulated and experimental results for experiments with a short electrolysis time. This numerical model was then used to study the influence of the flow velocity and the diffusion coefficient on the current density and on the average mass transfer around a wire a few microns in diameter. The general relation: S h p = 0.41 R e p 0.38 S h 0 .44 for 0.02

The influence of the fluid flow and the cell geometry on the deposition of copper on wires was studied numerically. A numerical method based on the system residual distribution schemes and the finite element method was developed to calculate the fluid flow and the mass transfer including the effects of diffusion, migration, convection, homogeneous reactions, turbulence and multiple electrode reactions in arbitrary shaped geometries. The k–ω model was used to calculate the turbulent fluid flow, and the turbulent Schmidt number is assumed equal to one. It was demonstrated that a downstream position of the anode yields a much more uniform deposition compared with an upstream placement of the anode. From calculations with different imposed currents, it was established that mass transfer only plays an important role if the current is above 70% of the limiting current. Furthermore, simulations with different flow rates, indicated that turbulent flow reduces the effects of mass transfer on the current density distribution.

The crack propagation rate of Type 304 stainless steel in diluted sulphuric acid solutions was modelled based on finite element calculations of the chemical and electrochemical conditions within the crack and an analytical expression for the crack-tip strain rate. The slip/dissolution/repassivation mechanism was assumed. The influence of various variables – dissolved oxygen, sulphuric acid content, stress intensity, crack length, temperature, flow rate, sensitization and yield strength – was studied and found to be in agreement with experimental observations. The model was calibrated against one data point. The effect of temperature on thermal conductivity, electrode reaction kinetics, equilibrium constants, yield strength and crack geometry was considered and the thermal activation energy for the crack propagation rate could almost fully be accounted for.

Anodizing of aluminium is an electrochemical surface treatment yielding the formation of an alumina film, the characteristics of the formed oxide strongly depending on the considered anodizing conditions. Heat transfer has an important influence on the anodizing process, which can be explained by considering the production of heat near the aluminium anode, combined with the significant influence of the local electrode temperature on the process of oxide formation. The influences of temperature and heat transfer on the growth of the anodic oxide film during anodizing of high purity Al are studied on a laboratory scale in a wall-jet electrode reactor. The impinging jet configuration of the reactor creates a non-uniformly accessible electrode with variable convection as a function of the radial position on the anode. The influence of the resulting nonuniform heat transfer on the local temperature of the electrode is monitored by local temperature measurements on the backside of the aluminium anode, whereas its influence on local film growth is evaluated by means of FEG-SEM surface and cross sectional analyses. A comparison between the simulated and experimentally acquired data is presented. The controlled and known electrolyte flow in the wall-jet reactor enable numerical simulations of the convection which supply additional information on the encountered conditions of heat transfer. The anodizing process itself is simulated using a model based on the high field theory.

A combined boundary element method (BEM)-finite element method (FEM) numerical approach is used for the simulation of current density and layer thickness distributions in a wafer plating reactor. The current and potential distribution effects due to the electrolyte resistivity are modeled with BEM, while the transient internal resistive 'terminal' effect of the wafer is modeled using FEM. A nonlinear Butler-Volmer type overpotential relation is considered to describe cathode kinetics. The declining internal wafer resistivity that is due to the growth of the initial copper seed layer, is modeled over a number of discrete time steps. Different contacting methods (4 or 8 contact points, ring contact) are investigated, and their terminal effect time is compared. The wafer consists of a ring-shaped current thief, with adjacent photoresist area's and a central electroactive patterned zone.

The residual distribution method is used to solve the multi-ion transport and reaction model in turbulent flow. The model describes the effects of convection, diffusion, migration, chemical reactions and electrode reactions on the concentration, potential and current density distributions in an electrochemical reactor. The Reynolds averaged Navier–Stokes (RANS) equations are used to calculate the turbulent flow, with the turbulent viscosity obtained from a low-Reynolds number k–ω model. Different turbulence models for the turbulent mass transfer are examined and validated in a parallel plate reactor for the deposition of Cu from an acid copper-plating bath. The most accurate turbulent mass transfer models are the algebraic model for the turbulent diffusion and the newly suggested model with the constant turbulent Schmidt number equal to 4.5. Furthermore, it is shown that the turbulence model for the mass transfer influences the local concentration distribution considerably but has much less effect on the current density distribution.

A versatile model for the simulation of transient multiion transport and reaction processes is applied to investigate current density distributions over a rotating disk electrode for linear voltammetric sweep experiments. The model accounts for ion transport by convection, diffusion, and migration, in combination with Butler-Volmer type electrode reactions. For several process conditions (reversible and irreversible reactions, excess or lack of supporting electrolyte), the current density distribution over the disk surface is examined and the transient current response is compared to results from the more commonly used one-dimensional axial approach. The impact of migrational effects on the nonuniform local process conditions over the disk surface is illustrated, and the resulting effect on the current peak height, width, and position is investigated. A mathematical correlation for the current peak height as a function of the reacting ion transference number is established.

Elsyca Plating Master, a new Solid Works based simulation tool to compute current density and deposit thickness distributions for electroplating processes, is presented. Complex three-dimensional shaped workpieces in arbitrarily designed plating cells can be modelled. The software enables optimising the cell design (e.g. anode, screen and current thief configuration) and working conditions (e.g. total current, pulse parameters) for a large variety of plating processes. Additionally, it provides the Production Department the analytical data to discuss the manufacturability of a product design with Design and Engineering. The application of Elsyca Plating Master for the prediction and optimisation of a chromium deposition process for complex three-dimensional parts is illustrated.

A versatile model for the simulation of electrochemical processes at a rotating disc electrode is presented. This model is based on the dilute solution ion model, in combination with an adequate description of electrode reaction kinetics. A brief introduction is given to the theoretical aspects of the model and the numerical solution technique being used to solve this model for the rotating disc electrode (RDE). A multiple ion electrolyte system with an excess of supporting electrolyte is considered. For several reaction conditions (reversible up to irreversible reactions) results of steady-state and linear sweep voltammetry simulations are presented and are compared with analytical and literature data. Based on computations of the current response, while sinusoidal varying potentials with different frequencies are applied, electrochemical impedances are also derived and compared with analytical results.

This article describes the calculation of the polarisation behaviour of a metal in an aqueous environment using a computational electrochemistry code based on finite elements. The corrosion system consisted of three parallel reactions (oxygen reduction, hydrogen evolution and metal dissolution), taking place in the centre at the surface of the rotating disc electrode (RDE). The selected problem is simple enough to be solved analytically, which allows verification of the finite element calculation. Simultaneously, the example is rich enough to demonstrate the potential and the advantages of finite element simulation for corrosion science and engineering. The analytical and finite element calculations were in excellent agreement. The influence of the speed of the RDE, of the bulk concentration of dissolved oxygen and of the bulk hydrogen ion concentration on the polarisation behaviour have been determined. The use of finite elements had the following specific advantages. Firstly, no prior assumption on the diffusion layer thickness had to be made. Secondly, transport by diffusion, convection and electro-migration were taken into account. Thirdly, the finite element approach is general and flexible enough to tackle more complex systems. The calculations presented here are a first step towards the finite element simulation of stress corrosion cracking of stainless steel in an aqueous nuclear environment.