Indian Journal of Chemical Technology Vol. 14, January 2007, pp. 16-21 Study of Schiff’s bases as surface modifiers for corrosion protection of copper in sulphuric acid Ganesha Achary, H P Sachin, Y Arthoba Naik * & T V Venkatesha Department of P. G. Studies and Research in Chemistry, School of Chemical Sciences, Kuvempu University, Shankaraghatta 577 451, India Email: drarthoba@ yahoo.co.in Received 14 February 2006; revised received 19 July 2006; accepted 6 September 2006 Surface modification of copper by newly synthesised Schiff’s bases, N- [(1E)-2-furylmethylene]-N-phenylamine (FA), 3-{[(1E)-2-furylmethylene] amino} phenol (FAP), 4-{[(1E)-2-furylmethylene] amino} benzoic acid (FAB) and 2-{(E)-[(3- hydroxyphenyl) imino] methyl} phenol (SAP), in 0.5 M sulphuric acid solution was investigated. The corrosion behavior of surface treated copper specimens was tested by galvanostatic polarization technique. The effect of concentration of Schiff’s bases in the treatment bath, treatment time and temperature of the corrosive medium on the corrosion protection efficiency of Schiff’s bases was investigated. Among the compounds studied, the protective film formed by FAB showed maximum protection efficiency. The inhibitive action of Schiff’s bases was due to their adsorption and consequent growth of the protective film on the metal surface. The inhibitive effectiveness depended strongly on the molecular structure of the Schiff’s base. The interaction of the compounds with the metal surface was confirmed by FTIR technique. The SEM studies showed the modification of copper surface due to the adsorption of Schiff’s bases. Keywords: Schiff base, Surface modifier, Copper corrosion, Sulphuric acid IPC Code: C07C251/00, C23F11/00 Copper is most commonly used material in heating and cooling systems because of its excellent thermal conductivity and good mechanical workability. However, the efficiency of the equipment is decreased due to the formation of scale and corrosion products on the surface. Therefore a periodic cleaning the surface is necessary which can be done by using pickling agents such as sulphuric acid and hydrochloric acids. These pickling agents not only attack the scale of corrosion products but also the metal surface. The undesirable destruction of metal surface can effectively be reduced by adding an effective corrosion inhibitor to the pickling solution. Commonly used inhibitors for copper corrosion are toxic compounds that should be replaced with the new eco-friendly inhibitors. Most of the inhibitors are derivatives of benzotriazole 1 , thiazole 2 , imidazole 3 etc. It is established that the lone pair of electrons on nitrogen and the protonation property of the azo and thiol groups are responsible for the formation of protective film on the metal surface and hence control the corrosion. The nature and stability of the film depends upon the molecular structure and geometry of the inhibitor. Diazonium salts form covalent bond with copper through its nitrogen 4 . Schiff’s bases are used as corrosion inhibitors in various corrosive media 5 for metals like zinc and iron. Schiff’s bases have been found to exhibit greater corrosion protection efficiency better than the corresponding aldehydes and amines 6 . The imine compounds are found to be suitable surface modifiers for the metals 7 . The present paper focuses on the use of Schiff’s bases of furfural and salicyladehyde with different substituted anilines, for surface treatment of copper against corrosion in sulphuric acid medium. The used compounds consist heterocyclic ring and an imine group with different substituents. The surface of copper was modified by immersion method. The influence of concentration of inhibitors was studied by electrochemical methods. Experimental Procedure All the chemicals used were of AR grade (s. d. fine chemicals, Mumbai, India). The Schiff’s bases, N-[(1E)-2-furylmethylene]-N-phenylamine (FA), 3-{[(1E)-2-furylmethylene] amino}phenol (FAP), 4-{[(1E)-2-furylmethylene] amino}benzoic acid (FAB) and 2-{(E)-[(3-hydroxyphenyl) imino] methyl} phenol (SAP), were prepared by adopting standard procedures 8 . The compounds were separated, recrystallised and the purity was confirmed by thin layer chromatography. The formation of the Schiff’s