Tannic acid as a corrosion inhibitor for zinc in different corrosive medium

This study investigates the potential of tannic acid as a corrosion inhibitor for zinc in three different corrosive mediums. The aims of this work are to determine the corrosion rate of zinc in different corrosive medium (HCl, NaOH and NaCl), evaluate the inhibition efficiency of tannic acid as corrosion inhibitor and investigate the corrosion effect via microscope. This work was performed through an analysis of tannic via FTIR, corrosion test and surface morphology study. Analysis of functional groups revealed the presence of many active components exists in the tannic acid such as O-H, C=O ester, C=C aromatic, C-H and C-O. Analysis of corrosion rate using weight loss measurement was found to vary significantly across the different environments. The highest corrosion rate was observed in 1M HCl (139.4 mm/yr), followed by 1M NaCl (3.21 mm/yr) and 1M NaOH (1.27 m/yr). Evaluation on the corrosion inhibition efficiency of tannic acid reveals that tannic acid effectively inhibited corrosion, with the highest inhibition efficiency of 94.9% observed in NaCl solution at a concentration of 0.2 g/L. In 1M NaOH solution, tannic acid at 1 g/L gives 74.19% inhibitor. Meanwhile, inhibitor efficiency of tannic acid in HCl shows 69.45%. Surface morphology revealed uniform corrosion in HCl, while localized corrosion was observed in NaOH and NaCl. In summary, tannic acid has shown different inhibitory effect in different medium. The corrosion inhibition efficiency by tannic acid was also concentration dependent. The study concludes that tannic acid is a promising corrosion inhibitor for zinc, particularly in neutral environments, and that its effectiveness varies depending on the corrosive medium.