Fluids

Fluids

Galvanic Corrosion – Fluent

    • lgarciactc
      Subscriber

      Hi all,

      I am trying to use Ansys Fluent 2020R1 to simulate a transient model of galvanic corrosion for a 2D couple consisting of iron and aluminium, and sea water as the electrolyte. I am having some trouble that makes me think something in the model is not well set.


      I am using the Species Model with volumetric and electrochemical reactions and species migration. The species of the model are Al+3, h2, oh- and h2o, and the solid species is Al.


      I have set the Tafel parameters (anodic and cathodic Tafel slopes, exchange current density and equilibrium potential) for each of the two electrochemical Reactions, have created a mechanism for each reaction and assigned the correspondent mechanism at the anode and cathode walls.

      The species boundary condition is set to “Zero diffusive flux” for all the species and walls, and the Potential boundary conditions are as follow:

    • Judy Cooper
      Ansys Employee
      Hi Igarciactc:
      The current flux or Potential value can be specified at a boundary, Since a potential gradient leads to a current flux, it is indirectly possible to specify the boundary condition you require by setting a zero-current flux at this boundary.
      All calculations should be run in double precision. Your result looks like there is something wrong with the boundary conditions. I have a similar case where voltage has the correct trend




    • lgarciactc
      Subscriber
      Thanks for the reply jcooper.
      We can indirectly specify the zero potential gradient based on ohmÔÇÖs law (current flux [A/m2] = - conductivity[S/m]*potential gradient[V/m]) because if potential gradient is 0 so does the current flux.
      The problem is in the anode and cathode walls, where the potential gradient is not 0. We want to obtain the potential gradient on the electrode surface. To obtain that we have to specify the Boundary Conditions in the anode and cathode walls as Flux Conditions [A/m2]. We are using a DEFINE_PROFILE UDF to specify the flux gradient in these walls but we get a segmentation error while accessing the x-component of the electric potential (UDS 0) with the command C_UDSI_G(f,t,0)[0].
      We are obtaining a contour for the Electric Potential (in the electrolyte) very similar to yours, but what we dont really understand is the plot of the Electrode Surface Potential (in the walls). If it is posible, could we see the Electrode Surface Potential that it is obtained in your model?
      We expect that the Electrode Surface Potential be equal to 0 in all the walls except in the anode-cathode walls (the opposite of the following plots).
      Thank you so much in advance!

    • lgarciactc
      Subscriber
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