The problem of determining oxidation products that result in a self-passivating phaseand an algorithm for its computational analysis-was recently discussed by Twyman et al. in this journal. To determine the oxidation reactions, they proposed a "greedy algorithm" for minimizing the total reaction enthalpy while conserving the stoichiometry of non-oxygen atoms, while allowing the addition of an arbitrary amount of oxygen. Greedy heuristics are commonly used in combinatorial optimization problems. Their heuristic ranks possible oxidation products by the relative oxidation enthalpy, then uses this ranking to prioritize possible degradation products. After determining the set of stable oxide products, one can apply the PBR to determine which materials self-passivate.