Applied Surface Science 256 (2010) 4370–4375 Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc Removal of tarnishing and roughness of copper surface by electropolishing treatment A.M. Awad a,∗ , N.A. Abdel Ghany b , T.M. Dahy c a Chemical Engineering and Pilot Plant Dept., National Research Centre, Dokki, Giza, Egypt b Physical Chemistry Dept., National Research Centre, Dokki, Giza, Egypt c Electron Microscope and Thin Films Dept., National Research Centre, Dokki, Giza, Egypt article info Article history: Received 14 September 2009 Received in revised form 9 February 2010 Accepted 9 February 2010 Available online 16 February 2010 Keywords: Electropolishing Anodic oxidation Tarnishing Brightness Roughness Leveling abstract Tarnishing and roughness of copper surface can be removed by electropolishing treatment (EP) imparting a bright and smooth surface at suitable conditions, e.g. current density, time, temperature, and viscosity. It was carried out by using an electrolytic cell containing phosphoric acid 55% as the electrolytic solution. Both copper working electrode and lead counter electrode, and reference electrode (SCE) were connected to a Potentiostat/Galvanostat to allow an electric current to pass through the solution. Some additives such as soluble starch, ethylene glycol, and methanol were added to reduce defects formed on the copper surface during EP process. The results showed that the highest gloss value was obtained by applying electric potential 1.5 V at the passive region of polarization curve. The surface was investigated after EP treatment, where SEM and EDX showed lower roughness in case of addition of both soluble starch and ethylene glycol more than methanol. Moreover, AFM analysis showed the lowest roughness in case of soluble starch more than other additives. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Chemical, physical and mechanical properties of copper make it the world third most widely used metal after iron and aluminum. It is used in very essential fields such as electrical applications, build- ing construction, industrial machinery, equipment, transportation, and consumer products [1]. Copper surface seems rough and complex under microscopic investigation, due to the presence of macro and micro scales of humps and depressions. The enhancement of surface smoothness requires removal of more than one micron of scratches (level- ing), while production of both smooth and bright surface requires removal of less than one micron of scratches, and then, a highly reflective surface is obtained [2]. Rough surface including humps and depressions allow contami- nants to be formed as traces of micro grams imparting a tarnish and matt appearance. Natural deposits lead to the tarnishing of copper surface, particularly, metal sulfide and carbonyl sulfide. Tarnishing of copper is formed by chemical reactions or adsorption of the envi- ronmental contaminations. It is highly influenced by the location of copper sheets and the environment, where the regions of sev- eral factories or crowded with transportation tools showed more tarnishing [3,4]. ∗ Corresponding author. Tel.: +20 238951623; fax: +20 233370931. E-mail address: awadx1@yahoo.com (A.M. Awad). Electropolishing technique (EP) is a highly efficient method for cleaning and brightening of metals and alloys. It has received much attention due to its practical and academic interests, some work- ers tried to attain bright and smooth surface of copper, aluminum, stainless steel, and other alloys by applying EP method [5–8]. For instance, Edson studied the brightening of copper, silver and gold by using an electrolytic solution composed mainly of thiourea and some additives such as polysaccharides as reducing materials and mineral acids as conductivity improvers. Also, Mayer explained the necessity to separate between anode and cathode by non- conductive slit to prevent the gas bubbles transfer to the anode surface and enhance the homogeneous distribution of electric cur- rent [9,10]. The process is diffusion controlled, depending on the concen- tration gradient forming a selective electrochemical dissolution and improving planarization efficiency of Cu surface, where the down and up thickness differences are eliminated [11,12]. It typi- cally occurs at the mass transfer limiting current at highly anodic potentials, where the metal surface is smoothed out. Simultane- ously, during EP process, some defects and pitting over the surface can be formed due to high evolution of oxygen gases adjacent to the surface at higher electric potential [13–15]. The limiting current value that determines the polishing effi- ciency depends on the rate of mass transfer of Cu 2+ ions from the diffusion layer to the bulk of the solution. The rate of mass transfer depends on the relative ionic movement, geometry of the anode, temperature, the type and physical properties of the electrolyte. 0169-4332/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2010.02.033