[luisvolumentres]

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 (BC.png):

BC.PNG

For these simulations I have seen in the literature that the boundary conditions at the walls are specified as gradients of the potential and not as a single potential value, so I wonder whether I can specify this BC in Fluent.
BC_example.PNG

Also, a floating point exception error has appeared many times. It has disappeared lowering the Under relaxation factor for the Faradaic current interface from 0.1 to 0.001 but then the residuals take too much time to reduce and do not lower more than e-10, which is a big value considering the order of the species mass fraction that is being calculated, around e-07.

error.PNG

For these conditions then I plot the contour of Electrode surface potential but it seems unreal that the potential at the walls is the one it’s being calculated.

contour.PNG

Could anyone with experience in this type of electrochemical models help? SOS

I would really appreciate any help!