The work presented in this review paper is part of a project to investigate corrosion degradation of steam generator (SG) tubing and tube support materials by sulfur compounds at reduced or intermediate oxidation levels (designated here as S-x). The stability of these S-x species in aqueous solutions is discussed, and the electrochemical and chemical interactions between S-x and metallic surfaces and the subsequent impact of these interactions on metal corrosion are reviewed. Factors influencing S-x-induced uniform corrosion, passivity breakdown and stress corrosion cracking (SCC) considered here include: pH, electrode potential, temperature, S-x species, alloy compositions and other impurity ions like Cl-. (c) The Author(s) 2019. Published by ECS.