Effect of Caffeine-Zn2+ System in Preventing Corrosion of Carbon Steel in Well Water

The inhibition efficiency (IE) of caffeine in controlling corrosion of carbon steel in well water in the absence and presence of Zn2+ has been evaluated by mass loss method. The formulation, consisting of 200 ppm of caffeine and 50 ppm Zn2+, offers 82% inhibition efficiency to carbon steel immersed in well water. Addition of malic acid increases inhibition efficiency of the caffeine-Zn2+ system. The inhibition efficiency of caffeine-Zn2+ and caffeine-Zn2+-malic acid system decreases with the increase in immersion period and increases with the increase in pH from 3 to 11. AC impedance spectra, SEM micrographs, and AFM studies reveal the formation of protective film on the metal surface. The film is found to be UV fluorescent.