The isothermal corrosion of Cr—1 Mo steel in superheated steam is approximated by the linear relationship W = W0 + Rt, where W0 and R are constants exhibiting inverse temperature dependences. Heat flux is accounted for by applying a constant factor of 1.5 to the corrosion rate of any isotherm. No correlation for corrosion in alkaline, deoxygenated water is offered, since data are sparse. Data indicate that, in an evaporator, Cr—l Mo steel corrodes at a rate of ∼2.5 × 10−3 cm/yr.