The proposal of an interaction potential between 180° Bloch walls and nonmagnetic obstacles, precipitates or pores, is presented. Use is made of the analogy between this phenomenon and the pinning of grain boundaries in polycrystalline materials. The model takes into account the increase of energy due to the flexibility of the boundary and it is applicable to low magnetization materials. Using this approach it is possible to calculate the coercive force and to compare it with early findings. The numerical values obtained are in agreement with the values we find in the literature with the advantage that the proposed potential is expressed in a simple analytical form.