We study the behaviour of the steady-state voltage potential in a material composed of a two-dimensional ob ject surrounded by a rough thin layer and embedded in an ambient medium. The roughness of the layer is supposed to be εα -periodic, ε being the magnitude of the mean thickness of the layer, and α a positive parameter describing the degree of roughness. For ε tending to zero, we determine the appropriate boundary layer correctors which lead to approximate transmission conditions equivalent to the effect of the rough thin layer. We also provide an explicit characterization of the polarization tensor as defined by Capdeboscq and Vogelius in [10]. This paper revisits the previous works of the author [17, 16, 11, 13], and it also provides new results for the very