CORROSION INHIBITION BY THE CAFFEINE - ZN~(2+) SYSTEM

摘要

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 Zn~(2+). In the presence of Zn~(2+), caffeine has excellent inhibition efficiency. A synergistic effect is noticed between caffeine and Zn~(2+). Synergism parameters have been calculated. The influence of pH on the IE of the caffeine - Zn~(2+) 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 Fe~(2+)-caffeine complex on the metal surface. The protective film has been analysed by Fourier transform infrared spectroscopy and fluorescence spectroscopy. The film consists of Fe~2+)-caffeine complex and Zn(OH)_2. It is found to be uv-fluorescent.