This first study deals with the one-dimensional (1D) problem of the scattering of electromagnetic waves by an obstacle coated with a thin ferromagnetic layer. Ferromagnetic materials have nonlinear behavior and are widely used in stealth technology as absorbing coatings. Our objective is the derivation, the stability analysis, and the numerical approximation of effective boundary conditions that permit simulation, at least approximatively, of the effect of the thin layer, avoiding the discretization of Maxwells equations inside this layer.