Corrosion and Corrosion-fatigue (CF) have long been recognized as the major degradation and failure mechanisms of engineering materials under combined mechanical loading and corrosive environments. How to model and characterize these failure phenomena and how to screen, rank, and select materials in corrosion and corrosion-fatigue resistance is a significant challenge in many engineering applications. In this paper, simple parameters for characterizing corrosion resistance of materials are proposed. For corrosion-fatigue, the mathematical structure of a superposition-theory based corrosion-fatigue model is investigated and possible closed-form and approximate solutions are sought. Based on the model and the associated solutions and test results, ranking of the materials in corrosion, fatigue, corrosion-fatigue, and related material design are discussed.