In this study, the evaluation of interfaces on iron boride Fe2B growth obtained by paste boriding process was carried out. Fractal geometry is used like a powerful tool for the roughness analysis present during iron boride growth. Experiments were performed in AISI 1045 steel at temperatures of 1193K for exposure times of 2, 4 and 6 h, and 1223K for treatment times of 2, 4, 5 and 6 h, varying the boron paste thicknesses in the range of 1 – 5 mm for each temperature and time. The fronts of the interfaces in iron boride coatings were characterized and digitized with mean of an optic microscope and Scion Image software. Self-affine methods were applied to the interface growths for validate the fractality of the system. It was established that the interface width, ω , scales to ω (L) ∼ L H , where H represents the roughness exponent of the boride layers.