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Electrochimica Acta 48 (2003) 4277–4289 Electrochemical investigation of dynamic interfacial processes at 1-octadecanethiol-modified copper electrodes in halide-containing solutions H.Y. Ma a,b,∗, C. Yangb , S.H. Chen a,c , Y.L. Jiao a , S.X. Huang a , D.G. Li a , J.L. Luob a Department of Chemistry, Shandong University, Jinan 250100, PR China b Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Canada T6G 2G6 c State Key Laboratory for Corrosion and Protection of Metals, Shenyang 110015, PR China Received 9 April 2003; received in revised form 4 August 2003; accepted 4 August 2003 Abstract 1-Octadecanethiol (C18SH) monolayers were self-assembled on the fresh and active copper surface pretreated by nitric acid etching method. The surface properties of the alkanethiol-modified copper electrode in halide-containing solutions were characterized systematically by using several electrochemical methods, including polarization curves, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN). The results show that C18SH self-assembled monolayers (SAMs) onto copper provide a flexible method that can protect the underlying copper against corrosion. With the immersion time of SAMs-coated copper electrode in NaCl and HCl corrosive solutions increasing, a slow loss of corrosion protection ability of SAMs indicates dynamic processes occurring at the electrode/solution interface and in the monolayers, such as expansion of the defects and transport of corrosive ions through defects of SAMs. Electrochemical noise (EN) is employed to detect the alkanethiol-modified copper surfaces immersed in HCl solution. This