The aims of this work were to investigate the effect and mechanism of improving industrial pickling by synergistic corrosion inhibition, as well as to propose a strategy for cleaner pickling. Using the methods of weight-loss, electrochemical polarization, and scanning electron microscopy (SEM) observation, it was revealed that an obvious effect was achieved through the synergistic inhibition of a complex-inhibitor composed of polyoxyethylene (20) sorbitan monolaurate (Tween-20) and KI in suitable proportions. These methods also confirmed that a monomolecular adsorption layer was formed on the metal surface, which provided an effective protection for the base metal. The adsorption was a spontaneous and exothermal process, and accorded well with the Langmuir isotherm. The formed adsorption layer on the metal surface was stable and compact. It also effectively retarded the hydrogen evolution on the cathode and the metal dissolution on the anode simultaneously, which indicated that the complex-inhibitor was a mixed-type inhibitor. On the basis of the inhibition effect, a simple and convenient method was proposed to evaluate the benefit of cleaner production with different additives.