85 Effect of Nano-TiO 2 Particles on the Corrosion Behavior of Chromium-Based Coatings M. Noroozifar * , M. Khorasani-Motlagh, Z. Yavari Department of Chemistry, University of Sistan & Baluchestan, Zahedan, I. R. Iran (*) Corresponding author: mnoroozifar@chem.usb.ac.ir (Received:28 Jan. 2013 and Accepted: 01 May 2013) Abstract: Nanosized TiO 2 particles were prepared by sol–gel method. The TiO 2 particles were co-deposited with chromium using electrodeposition technique. In investigating of coating surfaces by scanning electron microscope (SEM), the results showed that the morphology of the coating surface was changed by adding TiO 2 nanoparticles to the chromium coating. The corrosion behavior of the coatings was assessed by polarization technique in four media such as seawater, pipeline water, distilled water and 3.5% NaCl solution. The results showed that adding the TiO 2 nanoparticles into chromium coating, caused a decrease in current and rate of corrosion, and so increased the period of conservation from cupric undercoat. Keywords: TiO 2 Nanoparticles, Corrosion, Composite Coating, Chromium Electroplating, Tafel Curve. Int. J. Nanosci. Nanotechnol., Vol. 9, No. 2, June 2013, pp. 85-94 1. INTRODUCTION Copper and copper-based alloys are widely used in a great variety of applications, such as industrial equipment, building construction, electricity, electronics, coinage, ornamental parts, water treatment, etc [1]. Copper is widely used for tubing and piping in the distribution systems of drinking water throughout the world. Laws and standards have been issued in many countries to control copper levels in drinking water [2]. Corrosion of copper and its inhibition in a wide variety of media, particularly when they contain chloride ions, have attracted attention of a number of investigators [3]. Copper corrosion is the result of the loss of solid copper metal to solution. This occurs when electrons are lost by the base metal, and the solid phase is transformed into soluble, dissolved cuprous (Cu + ) and/or cupric (Cu 2+ ) ions. During metal corrosion in drinking water, chemical oxidation occurs at anodes where electrons are released. Alternately, chemical reduction (the gain of the electrons) occurs at the cathode [4]. Black chromium coatings are noteworthy as an alternative to either light chromium or black nickel deposits owing to their enhanced corrosion resistance. Traditional Cr-matrix coatings electrodeposited from Cr(VI) baths have been widely used for decoration and anti-corrosion. Electrodeposition of Cr(VI) needs to be replaced by another material system due to the intense toxicity and carcinogenicity of Cr(VI). Trivalent Cr plating is considered to be a promising replacement technology for hexavalent Cr plating [5]. Hexavalent chromium plating has been commercialized many years before. The main advantage of Cr(III) plating bath in comparison with a Cr(VI)-bath is that Cr 3+ ions are nontoxic environmentally benign[6]. Much attention has been focused on the development of ceramic/metal nanocomposites because such