Mixed self-assembled monolayers (SAM(mix)) were formed by 2-(Pyridin-2-yliminomethyl)-phenol (HL) and 1-dodecanethiol (DT) molecules on copper surface. The inhibitive ability of SAM(mix) in sodium chloride solution was characterized in situ by the scanning electrochemical microscope (SECM). The results show that the compactness and the stability of SAM(mix), formed by the two organic materials in an appropriate sequence, are improved and the inhibition efficiency (eta%) increases markedly. They also verify that SAM(mix) are formed due to the existence of collapsed sites and pinhole defects on SAMs of single materials on the surface of copper. The re-arrangement and the competitive adsorption of HL and DT molecules may have impact on the quality of SAM(mix). Possible structures of SAM(mix) are suggested based on the experimental results. (C) 2013 Elsevier Ltd. All rights reserved.