Corrosion protection of 1050 aluminium alloy using a smart self-cleaning TiO 2 –CNT coating A. Shadravan a , Z. Sadeghian b, ⁎, A. Nemati a , S.P. Mohammadi a a Department of Materials Science and Engineering, Sharif University of Technology, Azadi Street, P. O. Box 11155-4363, Tehran, Iran b Research Institute of Petroleum Industry (RIPI), West Blvd. Azadi Sport Complex, P.O. Box 14857-3311, Tehran, Iran abstract article info Article history: Received 11 March 2015 Revised 9 May 2015 Accepted in revised form 11 May 2015 Available online xxxx Keywords: TiO 2 –CNT Sol–gel Corrosion resistance Photocatalytic activity Inclusion of carbon nanotubes (CNTs) into the titanium dioxide coating on 1050 aluminium alloy was studied with the aim at enhancing the corrosion resistance of the surface. Composite coatings with various contents of CNTs were prepared via the sol–gel method and dip coating. XRD and FTIR phase and structural evaluations showed the presence of anatase phase in all thin films. Concomitant enhanced corrosion behaviour in the presence of CNTs was resulted from polarization potentiodynamic test. Band-gap evaluation was performed using absorbance spectra of coatings and showed considerable decrease of band-gap energy in the presence of CNTs. Photocatalytic properties and hydrophilicity of composite coatings were also analysed and evidenced the significant role of CNTs in obtaining the desirable photocatalytic and hydrophilic properties. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Titanium dioxide is the most promising semiconductor catalyst owning to its chemical and biological inertness, biocompatibility, excel- lent stability and non-toxicity [1–3]. Additionally, TiO 2 as an effective photocatalyst is capable of providing a self-cleaning surface [2–5]. Several techniques for obtaining TiO 2 thin films such as Electron Beam Evaporation, DC Magnetron Sputtering, Chemical Vapour Deposition and sol–gel process have been reported in literature [6–13] among which the vacuum techniques are suitable for small area substrates. Films obtained from these methods are non-stoichiometric and non- uniform and also costly equipment is needed. In contrast, sol–gel process is an industrially promising technique for the preparation of thin films on large area substrates as it offers advantages in terms of low consumption of energy, low material consumption rate, simplicity and speedy deposition on either small or large area substrates with good homogeneity requiring no expensive equip- ment [12–18]. In recent years, the application of TiO 2 –CNT nano-composites for environmental purification, such as decomposition of organic com- pound in polluted air and waste waters, has been increased [19,20]. It is believed that the enhanced catalytic property of TiO 2 in the presence of CNTs is due to providing a passage for transferring of electrons by CNTs [21]. Moreover, CNTs have a large specific surface area of approx- imately more than 150 m 2 g -1 leading to the absorption of organic and inorganic pollutants to the surface of TiO 2 –CNT composite that can be considered as a significant process of photocatalytic behaviour [22–25]. Considering the mentioned advantages of sol–gel process, fabrication of TiO 2 –CNT thin films via the sol–gel method has also been the subject of numerous investigations within the last decade [20,26–29]. The application of TiO 2 as a smart surface layer in order to mitigate the corrosion of metallic substrates has been also investigated [17,30–34]. It is reported that TiO 2 , as a chemically stable compound with excellent heat resistance, boosts the corrosion resistance of metallic substrates in two ways: firstly as a protective ceramic barrier on surface and secondly by means of a photo-generated current of cathodic protection occurring under UV irradiation [17,34]. In fact it is believed that TiO 2 acts as a photoanode providing the metallic electrode with generated conduction band electrons that promote the cathodic protection [35]. Aluminium has exceptional corrosion resistance thanks to the passive Al 2 O 3 layer developing rapidly on its surface; nevertheless, this metal suffers low resistance against pitting corrosion especially in onshore environment. TiO 2 coating, especially in the form of nano-TiO 2 , is reported to enhance corrosion resistance of aluminium in seawater [36,37]. This investigation is focused on fabrication and characterization of TiO 2 –CNT thin films as a novel corrosion preventer with proved excellent photocatalytic activity on aluminium 1050 alloy via sol–gel method. The effect of inclusion of CNTs on corrosion resistance of the coating has been also evaluated. Surface & Coatings Technology xxx (2015) xxx–xxx ⁎ Corresponding author. E-mail address: sadeghianz@ripi.ir (Z. Sadeghian). SCT-20267; No of Pages 8 http://dx.doi.org/10.1016/j.surfcoat.2015.05.015 0257-8972/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Please cite this article as: A. Shadravan, et al., Corrosion protection of 1050 aluminium alloy using a smart self-cleaning TiO 2 –CNT coating, Surf. Coat. Technol. (2015), http://dx.doi.org/10.1016/j.surfcoat.2015.05.015