Corrosion Module UpdatesFor users of the Corrosion Module, COMSOL Multiphysics ® version 5.2a brings a new External Short boundary condition that is useful for corrosion protection problems that involve interconnecting large, electrochemically active objects. Additionally, a new tutorial model studies how the cathodic protection of a monopile device decreases as its sacrificial anodes dissolve over time. Review all of the updates to the Corrosion Module in more detail below.
New Nernst-Planck-Poisson Equations Interface
The new Nernst-Planck-Poisson Equations multiphysics interface can be used to investigate charge and ion distributions within an electrochemical double layer, where charge neutrality cannot be assumed. The Nernst-Planck-Poisson Equations interface adds theElectrostatics and Transport of Diluted Species interfaces to a model, together with predefined couplings for potential and space charge density.
The concentration of a cation (blue) and an anion (green) close to the electrode surface at x = 0. The sum of charges deviates from 0 close to the surface, forming a diffuse-charged double layer.
New External Short Boundary Condition
The new External Short boundary condition lets you short circuit Electrode Surfaces, Porous Electrodes, and Electrodes through an external lumped resistance. The new boundary condition is suitable for studying short circuiting in batteries, for instance, or for interconnecting large, electrochemically active objects in corrosion protection problems.
New Electrochemical Heat Source Multiphysics Node
The new Electrochemical Heat Source multiphysics interface offers an optional way to couple the electrochemical heat sources with a heat transfer interface.
New Thermodynamic Equilibrium Kinetics Type
Electrode reactions now support a new Thermodynamic Equilibrium electrode kinetics type (known as Primary Condition in the Secondary Current Distribution interface), which assumes zero overpotential (negligible voltage losses).
New Support for Film Resistance and Dissolving-Depositing Species in Porous and Edge Electrodes
The Porous Electrode and Edge Electrode nodes now support the addition of Film Resistances and Dissolving-Depositing Species. Previously, this was only supported in the Electrode Surface feature. Film resistances and dissolving-depositing species in porous electrodes can, for instance, be used to model solid-electrolyte-interphase (SEI) formation in lithium-ion batteries.
New Tutorial Model: Monopile with Dissolving Sacrificial 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.
Application Library path for the Monopile with Dissolving Sacrificial Anodes tutorial model:
The electrode surface potential of the upper part of an offshore wind turbine foundation (monopile). The surrounding sacrificial anodes dissolve, reducing the cathodic protection capabilities of the installation over time.