Natural corrosion inhibitors derived from powder, concentrated extract and tannin of ketapang (Terminalia catappa L.) leaves for iron protection in sodium chloride solutions

Tannin as one of the organic corrosion inhibitors is generally used in the form of pure compounds. This makes the production of tannin inhibitors more complex. The use of tannin inhibitors can be replaced by maintaining the compound in powder or extract form. This study aims to determine the ability of powder, concentrated extract and tannin obtained from ketapang leaves as iron corrosion inhibitors in 3 % sodium chloride (NaCl) solution. The novelty of this study lies in the use of ketapang leaves powder as corrosion inhibitor which has not been previously investigated, as a sustainable and simpler form of corrosion inhibitor to address the challenge. This inhibition process was carried out by considering the amount of inhibitor and the duration of immersion. The addition of 2 % was applied over 2 days, 4 days, 6 days, and 8 days. The corrosion rate of iron plate was calculated using the mass loss method, and then continued with the calculation of the inhibition efficiency. The results obtained on the 8 days showed differences in corrosion rate and inhibition efficiency for each form of inhibitor. The use of ketapang leaves powder gave a corrosion rate of 3.73 mpy and an inhibition efficiency of 84.88 %, the use of concentrated extract gave a corrosion rate of 0.93 mpy and an efficiency of inhibition of 96.22 %, and the use of tannin gave a rate of corrosion of 0.62 mpy and an inhibition efficiency of 97.48 %. Therefore, ketapang leaves can be used in all three form, especially the powder form offering practical that inhibits corrosion of iron.