A critical model of water-oil surfactant distribution has been developed and validated for the evaluation of mixed surfactant partitioning and distribution in water-oil environments. The surfactant distribution model, which is a combination of surfactant partitioning sub-model, partitioning coefficient calculation method, and a developed critical micelle concentration (cmc) prediction sub-model based on previous work, provides a very powerful tool to evaluate the partitioning of mixed surfactants in water-oil environments. Different methods to calculate partitioning coefficients are introduced, which includes transfer free energy method and group contribution method. The partitioning data from model prediction and from experiment agree very well. The mixed micelles start to form in water-oil environments only after the apparent cmc is reached during partitioning. The selective partitioning of one particular surfactant in mixed surfactants can be explained by its apparent cmc which is interpreted as one characteristic of the hydrophobicity/hydrophilicity of that surfactant in water-oil environments. It is believed that the partitioning and distribution of non-homologous mixed surfactants in oil-water environments are evaluated theoretically and experimentally for the first time. The effect of partitioning on corrosion inhibition of mixed surfactants was initially evaluated by modified Langmuir adsorption and by electrochemical measurements. The corrosion inhibition efficiency from model prediction and from experimental measurements is comparable. The use of surfactant inhibitors has received extensive attention in the oil and gas industry for corrosion inhibition of production and transportation pipes (metallic materials, such as steel and copper) in a way that surfactant molecules usually adsorb on steel surface and form a protective film which acts as a barrier to prevent corrosive media penetration and attack. [1][2][3][4] Compared to the production and use of pure surfactants, surfactant mixtures are well known due to the superior physicochemical properties and capabilities in efficient solubilization, adsorption, suspension, and transportation. [5][6][7][8] The solutions of surfactant mixtures can often be conveniently tuned to achieve desired properties by adjusting the mixed surfactant types and molar ratios. More surface-active and expensive surfactants are often mixed with less surface-active and cheaper surfactants to reduce cost.9,10 Natural mixtures of surfactants are sometimes used to avoid the investment in separation processes. However, further studies are required in order to optimize inhibition efficiency of surfactant mixtures and minimize environmental impact.Surfactant molecules have hydrophilic and hydrophobic sections, 7,11,12 which are critical to the adsorption on metal surface and associated corrosion inhibition.2-4 The hydrophilic functional group of surfactant molecules strongly prefers interaction with polar entities such as metals, which is helpful in corrosion inhibition. The hydroph...