Armco iron samples boronized at 850 and 1000° C in crystalline boron powder have been studied. Scattering and transmission Mossbauer measurements, supported by optical and electron scanning metallography and by X-ray diffraction analysis, enabled the surface phases to be identified, the multi-layer structure of the coatings to be defined and the average thickness of each layer to be measured. In addition to an inner Fe2B layer and to an intermediate FeB layer, the presence of an outer layer of a third phase richer in boron that FeB has been ascertained in the boride coatings. The morphology of the reaction products and their mechanical consistency have also been examined and discussed.