On the basis of experimental results exhibited in Part I, a reaction model of the dissolution—passivation process of FeCr alloy in acidified sulfate media is proposed. This reaction mechanism of alloy is considered as that of Fe perturbed by the Cr addition. However, the change in the dissolution—passivation process of Fe alone is not sufficient to interpret the whole results. Hence, firstly an interaction between adsorbed species was introduced: a chromium passivating species hinders drastically the rate of the Fe(II)ads→ Fe(II)sol dissolution path. Finally, it was also considered that the uniform dissolution of alloy is accounted for by the change of the surface concentration of alloy elements. The proposed model interprets satisfactorily the experimental results.