The corrosion behavior of three steels in high temperature water was compared: a cast martensitic steel (CA-6NM ACI CA-6NM) 403 stainless steel (UNS S40300) and a low alloy steel (HY 80 ASTM A-508). Test specimens were exposed to mildly alkaline solution at 500 ºF for up to 5000 hours. Several surface conditions were used including chemically passivated and electropolished surfaces. The corrosion films consisted of ferrite spinel crystals (AFe2O4) with some basal chromite spinel (ACr2O4) for the steels with higher Cr content. Total corrosion and corrosion product release were also quantified using chemical descaling. The corrosion rates were more than an order of magnitude greater than those of Ni-based alloys tested previously and greater than that of 304 stainless steel. Relative comparisons of the rates are interpreted in terms of the base alloy composition and surface treatment.