Corrosion Module Updates

For users of the Corrosion Module, COMSOL Multiphysics® version 5.5 brings a Current Distribution, Pipe interface, an interface for equilibrium potential calculation using the Nernst equation, and concentration-dependent Butler–Volmer kinetics from chemical equations. Read more about the corrosion news below.

Current Distribution, Pipe Interface

A new Current Distribution, Pipe interface has been added to model internal pipeline corrosion. The interface solves for the internal electrolyte potential inside virtual tubes of a specified radius along edges in a 3D geometry. Due to the tangential formulation of the charge balance equation along the edges, the computation time and resources are significantly reduced, compared to modeling the corresponding problem in a full 3D geometry. Corrosion protection system modeling is facilitated by the tailor-made Pipe Point Sacrificial Anode feature. You can see this new interface demonstrated in the Pipeline Corrosion Protection Using Resistor Controlled Cathodic Protection model. The new interface can for instance be used for designing corrosion protection systems in the process industry.

A piping system model visualizing the pipe potential with many red areas to indicate the highest potentials and least protected parts. Piping system Pipe potential in a piping system that is protected by sacrificial anodes. The red areas indicate the highest potentials, revealing the least protected parts.

Equilibrium Potential Calculation Using the Nernst Equation

In the Electrode Reaction and Porous Electrode Reaction features, the equilibrium potential of electrode reactions can be defined using the new Nernst Equation option, making it easier to set up thermodynamically consistent models. In physics interfaces solving for multiple concentrations, such as the Tertiary Current Distribution and Chemistry interfaces, the equilibrium potential will automatically be concentration dependent, based on the reaction stoichiometry. All models in the Application Libraries featuring Nernstian equilibrium potentials have been updated to use the new feature.

The Porous Electrode Reaction feature settings with the Equilibrium Potential section open and the Nernst equation selected. Porous Electrode Reaction feature: Equilibrium Potential Settings section for the Equilibrium Potential in the Tertiary Current Distribution, Nernst-Planck interface. The equilibrium potential will be calculated automatically from the reaction stoichiometry and species concentrations.

Concentration-Dependent Butler–Volmer Kinetics

In the Electrode Reaction and Porous Electrode Reaction features, the exchange current density of the Butler-Volmer and Linearized Butler-Volmer kinetics expressions can now be automatically defined to be concentration dependent, based on reaction stoichiometry. The option is available if the Nernst equation option is used when defining the equilibrium potential. In the Tertiary Current Distribution, Nernst-Planck interface, the options Mass action law and Lumped multistep are available for the exchange current density type. All models in the Application Libraries featuring Nernstian equilibrium potentials and concentration-dependent kinetics have been updated to use the new feature.

The Porous Electrode Reaction feature settings with the Electrode Kinetics section open and the Butler-Volmer expression type selected. Porous Electrode Reaction feature: Electrode Kinetics Settings section for the Electrode kinetics in the Tertiary Current Distribution, Nernst-Planck interface. The exchange current density will be calculated automatically from the reaction stoichiometry and species concentrations.

Chemistry Interface Support for Electrode Reactions

The Chemistry interface, added to the Corrosion Module in version 5.5, now features Electrode Reaction and Electrode Reaction Group features. The Chemistry interface allows for defining multiple species and electrode reactions, as well as ordinary chemical reactions. Additionally, mixture and thermodynamic properties, such as equilibrium potentials, can be calculated automatically by the Chemistry interface. Variables defined by these features, such as local current densities and equilibrium potentials, can be coupled to any other applicable physics interface.

The settings for the Electrode Reaction feature when two Chemistry interfaces are used. Electrode Reaction feature: Chemistry interfaces Two Chemistry interfaces are used in this model to define the equilibrium potentials and kinetics of the reactions in a solid oxide water electrolyzer.

New Adsorption Models

The Transport of Diluted Species in Porous Media and Transport of Diluted Species in Fractures interfaces include two new adsorption isotherms to predict the adsorption of dissolved species onto porous media. The Brunauer–Emmett–Teller (BET) and Toth isotherms are added to the existing Langmuir and Freundlich isotherms.

New Tutorial Model

Version 5.5 brings a new tutorial model.