An FeS electrode was prepared by spark plasma sintering, and FeS was demonstrated for the first time to be cathodic compared with steel in a liquid environment. The effect of suspended amorphous iron sulfide (FeS) particulates on the corrosion behavior of carbon steel in aqueous H2S environment was investigated via corrosion tests and electrochemical techniques. Results revealed that FeS formed preferential cathodic sites with a low overpotential, which favored hydrogen evolution. This phenomenon led to the formation of microgalvanic cells between FeS and steel and the selective dissolution of steel. Adsorbed FeS accumulated and combined with adjacent FeS particles to form large crystals of approximately 100 mu m. The formation of large corrosion products contributed markedly to the sharp increase in corrosion rate. The interaction between H2S and FeS particulates resulted in serious steel corrosion and changed the transformation of corrosion products.