International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 197 118401-5353 IJET-IJENS © February 2011 IJENS I J E N S A Photo-Cathodic Protection System Utilizing UV Radiations Intesar Ahmed*, Zaki Ahmad**, Faheemuddin Patel**, M. Shuja Khan* **Mechanical Engineering Department, **King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia *Department of Electrical Engineering, *COMSATS Institute of Information Technology, Lahore, Pakistan Email: *drintesarahmad@ciitlahore.edu.pk , **ahmadz@kfupm.edu.sa Abstract - Metallic corrosion of steel can be successfully prevented by using a TiO 2 based photo-electrochemical system under UV radiations. A TiO 2 semiconductor in a scavenging medium (water or formate) generates photocurrent and shifts the potential of steel to more negative values. This paper describes a cathodic protection system using a TiO 2 photoanode. The system has a potential to be developed for field applications because it is capable of fulfilling the dual functions of both cathodic protection as well as environmental cleaning. Keywords: UV radiation, Photo-electrochemical process, TiO 2 , C.B (Conduction Band). 1. INTRODUCTION Corrosion is a major threat to the integrity of costly hydrocarbon assets such as onshore and offshore plants, transport pipelines, infrastructure and process systems and its devastating regimes extending to critical assets, utilities and buildings as well. Cathodic protection and coatings are the two largest contributors to the direct cost of corrosion, which shows the importance of these techniques to mitigate corrosion. In cathodic protection, a substantial progress has been made which is shown by the development of computerized surveillance and mitigating techniques for AC and DC couplings [1]. New anodes comprising of conductive ceramic tubes or cylinders of metal matrix oxide composites (MMC) coated with titanium solid in mesh form are being produced. With the emergence of nanotechnology and increasing demand on green environment, investigations have been undertaken to study the photocatalytic effect of titanium dioxide [2-5]. Photo- electrochemical techniques of corrosion prevention of steel and have been suggested [6-12]. Studies undertaken in recent papers have shown that the cathodic protection of steel by TiO 2 under UV illumination is highly promising. This system offers a method of galvanic system without anode consumption. Photocathodic protection using n-TiO 2 (Nanostructured TiO 2 ) film on a steel substrate has shown to clean the environment while protecting the structural integrity because of photocatalytic properties of TiO 2 [7]. This paper describes the design of a novel multi functional cathodic protection system using n-TiO 2 photoanode. 2. THEORY OF PHOTOCATHODIC PROTECTION The basic idea of photocathodic protection is to replace the sacrificial anodes such as Mg, Zn or Al with a semiconductor such TiO 2 and ZnO photoanodes that generate CB electrons upon band gap irradiation (Fig. 1). The principle is to use the reductive energy of photo-exited electrons in the UV irradiated TiO 2 an n-type semiconductor. On contact with steel, the electrons are injected to the metal being protected via conduction band. Hence, the potential of the steel can be polarized in a direction more negative than the flat band potential of TiO 2 . If the potential is kept more negative than the corrosion protection of steel, it can be protected [3, 13]. When TiO 2 was galvanically connected to a steel electrode in the absence of light the mixed corrosion potential was close to the Ecorr of steel. However, on illuminating by UV radiations, the TiO 2 electrode became more negative than steel because of photo-generated electrons. The counter reaction is the oxidation of water or any organic contaminants by photo-generated holes but not the oxidation of TiO 2 . Hence, TiO 2 photoanode would continuously discharge current without being consumed unlike the conventional Zinc or Magnesium anodes. This makes it an attractive candidate as non-sacrificial anode [5]. Figure 1. Photocatalytic effect- Release of electrons and holes and production of OH - radicals.