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A steel structure immersed in seawater is protected from corrosion through 40 sacrificial anodes. This example models the potential distribution at the surface of the protected structure assuming a constant limiting current for oxygen reduction at the protected surface.
Corrosion costs the world upwards of $1 trillion each year. Most corrosion occurs due to electrochemical reaction processes taking place underwater and in wet or humid environments. The Corrosion Module allows engineers and scientists to investigate these processes, gain an understanding of the extent to which corrosion could occur over the lifetime of a structure, and implement preventative measures to inhibit electrochemical corrosion, in order to protect their structures. The module can be used to simulate corrosion at the microscale in order to investigate the fundamental mechanisms, and at larger scales to determine how to protect massive or long-ranging structures from corroding.
The Corrosion Module includes features, interfaces, and example models that enable a straightforward approach to the simulation of all electrochemical corrosion processes, such as galvanic, pitting, and crevice corrosion. Transport in corrosive and corroded material is accounted for through the dynamic modeling of changes in the corroding surface and the electrolyte in contact with such surface. The Corrosion Module includes standard interfaces for modeling the corrosion potential and current distributions of corrosion processes where the electrochemical reaction kinetics can be described by the Tafel, Butler-Volmer, or other user-defined equations. The electrochemical reactions are fully resolved together with electric potentials in electrolytes and metal structures, homogeneous chemical reactions, and phenomena unique to corrosion processes such as the change of the shape of a metal surface due to corrosion.
Cyclic voltammetry is a common analytical technique for investigating electrochemical systems. In this method, the potential difference between a working electrode and a reference electrode is swept linearly in time from a start potential to a vertex potential, and back again. The current-voltage waveform, called a voltammogram, provides information about the reactivity and mass transport properties of an electrolyte.
The purpose of the app is to demonstrate and simulate the use of cyclic voltammetry. You can vary the bulk concentration of both species, transport properties, kinetic parameters, and the settings of the cyclic voltammeter.
This model simulates atmospheric galvanic corrosion of an aluminum alloy in contact with steel. The electrolyte film thickness depends on the relative humidity of the surrounding air and the salt load density of NaCl crystals on the metal surface. Empirical expressions for the oxygen diffusivity and solubility are also included in the model in order to derive an expression for the limiting oxygen reduction current density.
Steel structures immersed in seawater can be protected from corrosion through cathodic protection. This protection can be achieved by an impressed external current or by using sacrificial anodes. The use of sacrificial anodes is often preferred due to its simplicity. This example models the primary current distribution of a corrosion protection system of an oil platform using sacrificial aluminium anodes.
A monopile foundation is a large-diameter structural element that can be used to support structures like offshore wind turbines. This application exemplifies how the cathodic protection of a monopile decreases over time as the sacrificial anodes dissolve. The model can be used to evaluate secondary current distribution electrode kinetics on the protected steel structure by taking into account the simultaneous electrochemical reactions that lead to metal dissolution and oxygen reduction (mixed potential).
The monopile geometry consists of an upper component with a coated steel surface and a lower uncoated steel pipe. It is also surrounded by either seawater or mud, with differing Tafel expression reaction kinetics used for these different environments. The tutorial model is solved using a time-dependent study for a time period of 12 years. Two cases are investigated: when the whole monopile is grounded, and when the transition piece is grounded and the lower pipe is connected to the transition piece through a lumped resistance.
The model also uses the new customized Sacrificial Edge Anode subnode for modeling slender sacrificial anodes along geometric edges, which is now available in the Secondary Current Distribution interface. The subnode enables you to model the changing cathodic protection properties of the anodes as they dissolve in time-dependent simulations.
Impressed current cathodic protection is a commonly employed strategy to mitigate the ship hull corrosion where an external current is applied to the hull surface, polarizing it to a lower potential. In this model, the effect of propeller coating on the current demand is demonstrated.
This tutorial example serves as an introduction to the Corrosion Module and models the metal oxidation and oxygen reduction current densities on the surface of a galvanized nail, surrounded by a piece of wet wood, which acts as electrolyte. The protecting zinc layer on the nail is not fully covering, so that at the tip of the nail the underlaying iron surface is exposed. First the electrolyte conductivity and the electrode reaction kinetics are modeled to obtain a secondary current distribution (concentration variations in the cell are not accounted for), in a second part the oxygen transport is included to model a tertiary current distribution.
This model exemplifies the basic principles of crevice corrosion and how a time-dependent study can be used to simulate the electrode deformation. The model is in 2D and the polarization data for the corrosion reaction is taken from a paper by Absulsalam and others.
The model and the results are similar to a 1D model by Brackman and others. This model does not account for mass transport effects. For a more detailed treatment of mass transport in a crevice, see the Crevice Corrosion of Iron in an Acetic Acid/Sodium Acetate Solution model example.
This example models cathodic protection of a steel reinforcing bar in concrete.
Three different electrochemical reactions are considered on the steel surface. Charge and oxygen transport are modeled in the concrete domain, where the electrolyte conductivity and oxygen diffusivity depend on the moisture content.
The impact of different moisture levels on the corrosion currents is investigated.
Electrochemical impedance spectroscopy (EIS) is a common technique in electroanalysis. It is used to study the harmonic response of an electrochemical system. A small, sinusoidal variation is applied to the potential at the working electrode, and the resulting current is analyzed in the frequency domain.
The real and imaginary components of the impedance give information about the kinetic and mass transport properties of the cell, as well as the surface properties through the double layer capacitance.
The purpose of the Electrochemical Impedance Spectroscopy analysis app is to understand EIS, Nyquist, and Bode plots. The app lets you vary the bulk concentration, diffusion coefficient, exchange current density, double layer capacitance, and the maximum and minimum frequency.