The Pb-Sb alloy consists of alpha-Pb crystals and eutectic phase. On anodic polarization of Pb-Sb electrodes in H2SO4 these phases are oxidized forming PbSO4 and lead oxides : PbO, PbO(n), PbO2 as well as Pb1-xSb(x)O, Pb1-xSb(x)On, Pb1-xSb(x)O2. The potential regions of formation of the above phases have been determined through x-ray diffraction analysis as well as their stability and the effect of antimony on the boundaries of these potential regions. It has been established that antimony facilitates the appearance of a potential region between 0.8 and 1.2 (1.3) V in which nonstoichiometric Pb1-xSb(x)O(n) is formed. This leads to a shift in the potential of oxidation of PbSO4 to PbO2 from 1.0 V for Pb electrodes to 1.2 (1.3) V for Pb-Sb ones. The reason for the formation of Pb1-xSb(x)O(n) (which has the same crystal structure as that of tet-PbO or is amorphous) has been investigated. It has been established that antimony has a catalytic effect on the reaction PbO --> PbO(n) and slows down the rate of reaction PbO(n) --> PbO2. It has been proven experimentally that antimony increases the degree of hydration of lead dioxide from 10% (for Pb electrodes) to 30% (for Pb-20% Sb electrodes). This leads to the formation of elastic elements in the structure of the corrosion layer which, in their turn, reduce cracking of the corrosion layer.