  We are interested in a reduced model for corrosion of iron, in which ferric
cations and electrons evolve in a fixed oxide layer subject to a
self-consistent electrostatic potential. Reactions at the boundaries are
modeled thanks to Butler-Volmer formulas, whereas the boundary conditions on
the electrostatic potential model capacitors located at the interfaces between
the materials. Our model takes inspiration in existing papers, to which we
bring slight modifications in order to make it consistent with thermodynamics
and its second principle. Building on a free energy estimate, we establish the
global in time existence of a solution to the problem without any restriction
on the physical parameters, in opposition to previous works. The proof further
relies on uniform estimates on the chemical potentials that are obtained thanks
to Moser iterations. Numerical illustrations are finally provided to highlight
the similarities and the differences between our new model and the one
previously studied in the literature.
