Abstract Unexpected corrosion problems that arose in a crystallization plant with evaporators made entirely of type 316L (UNS S31603) stainless steel (SS) were solved using a corrosion inhibitor system of ethylenediaminetetraacetic acid (EDTA)-hydroxylamine sulfate (Sl)-iron anions (Fe2+). An experimental statistical plan reduced the number of experiments needed to optimize the concentration of EDTA-Sl-Fe2+. Moreover, the plan allowed more rapid and economical study of the action of each component in the inhibition mechanism. Statistical processing of the data collected from the potential-vs-time, anodic, and cathodic potentiodynamic measurements permitted estimations of the influence of each independent variable (EDTA, Sl, and Fe2+concentrations). Voltammetric, polarographic, anodic potentiodynamic curves, and Flade potential measurements helped further understanding of the inhibiting system.