Corrosion inhibition by the caffeine -: Zn2+ system

The inhibition efficiency (IE) of caffeine, in controlling corrosion of carbon steel immersed in neutral aqueous solution has been evaluated by the weight loss method, in the absence and presence of Zn2+. In the presence of Zn2+, caffeine has excellent inhibition efficiency. A synergistic effect is noticed between caffeine and Zn2+. Synergism parameters have been calculated. The influence of pH on the IE of the caffeine - Zn2+ System has been investigated. As the pH value decreases, the inhibition efficiency also decreases. The rate of dissolution of the metal seems to be faster than the rate of diffusion of the inhibitors towards the metal surface and the formation of Fe2+-caffeine complex on the metal surface. The protective film has been analysed by Fourier transform infrared spectroscopy and fluorescence spectroscopy. The film consists of Fe2+-caffeine complex and Zn(OH)(2). It is found to be uv-fluorescent.