The role of indole and its derivatives in the pitting corrosion of Al in neutral chloride solution A.A. El-Shafei a, * , S.A. Abd El-Maksoud b , A.S. Fouda a a Department of Chemistry, Faculty of Science, El-Mansoura University, ET 35516 El-Mansoura, Egypt b Department of Chemistry, Faculty of Education, El-Arish, Sinai, Egypt Received 28 August 2002; accepted 4 March 2003 Abstract The ability of indole and its derivatives to protect aluminium against pitting corrosion was studied using potentiodynamic polarization technique. The order of inhibition effect of these compounds was found to be tryptamine (II) > tryptophane (III) > indole (I). The current decay measurements were used to confirm the inhibiting characteristics and the order of inhibition effect of these compounds. The inhibition properties of these compounds were discussed ac- cording to their adsorption on Al surface. The inhibition efficiency was found to be depending upon the number of active centres, molecular size and the mode of adsorption. The effect of preadsorbed film of these compounds on the pitting corrosion of Al was also studied. Finally, their influence on the ethanol oxidation was tested using cyclic voltammetric technique. The results were discussed and correlated to the their inhibition properties towards Al pitting corrosion. Ó 2003 Published by Elsevier Ltd. Keywords: Aluminium; Pitting corrosion; Platinum; Inhibition; Ethanol oxidation 1. Introduction The many important applications of aluminium and its alloys have resulted in research into its electrochemistry behaviour and corrosion resistance in a wide variety * Corresponding author. Fax: +20-50-346781. E-mail address: elshafeiaalaa@maktoob.com (A.A. El-Shafei). 0010-938X/$ - see front matter Ó 2003 Published by Elsevier Ltd. doi:10.1016/S0010-938X(03)00067-2 www.elsevier.com/locate/corsci Corrosion Science 46 (2004) 579–590