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We have performed all-atom classical molecular dynamics simulations of aggregation and adsorption of different corrosion inhibitor molecules on metal surfaces. We report free energies of aggregation and adsorption of imidazolinium-type (henceforth referred to as imid) and quaternary ammonium-type (referred to as quat) corrosion inhibitors of different alkyl tail lengths. Corrosion inhibitor molecules show a strong tendency to adsorb onto metal surfaces in the unaggregated state. Inhibitor micelles, on the other hand, experience a free energy barrier to adsorption. The quat micelles are found to be thermodynamically stable in the adsorbed state whereas the imid micelles are only metastable in the adsorbed state. Quat micelles deform and partially disintegrate upon adsorption, which renders stability, while the imid micelles do not deform. The inhibitor molecules demonstrate a strong tendency to aggregate into micelles in the aqueous phase. The micellization free energy is found to be ~68 kBT for a micelle comprising of 18 molecules of imid molecules.