Comparative corrosion resistance of aluminum in NaCl and HCl medium using salam leaves (Syzygium polyanthum) extract as corrosion inhibitor

• R. Tambun¹, A.H. Sofian², M.T.A. Fath¹, V. Alexander¹, T. Napitupulu¹ and A. Manurung¹

¹ Department of Chemical Engineering, Faculty of Engineering, Universitas Sumatera Utara, Jl. Almamater Kampus USU, Medan, 20155, Indonesia
² Faculty of Chemical and Process Engineering Technology, Universiti Malaysia Pahang Al-Sultan Abdullah, 26300 Gambang, Pahang, Malaysia

Abstract: This study aims to compare the corrosion resistance of aluminum using tannin extracted from Syzygium polyanthum leaves in HCl and NaCl medium. The research stages included the extraction of Syzygium polyanthum leaves using the microwave-assisted extraction (MAE) method, tannin isolation, and corrosion resistance analysis. Tannin was extracted from salam leaves powder using MAE with 70% ethanol solvent (ratios of 1:6, 1:8, 1:10, and 1:12 g/mL), then separated using ethyl acetate to obtain pure tannin. The results showed that the highest extract yield of 16.88% was obtained at a sample to solvent ratio of 1:12 g/mL, which contained the highest tannin concentration of 30.242 mg TAE/g or 3.024%, and this extract was used as a corrosion inhibitor. Aluminum plates were immersed in 3% NaCl and 3% HCl solutions with and without the addition of 3% tannin obtained from the 1:12 g/mL ratio. The corrosion rate of aluminum in 3% HCl medium on the 12th day was 21.9 mpy (without inhibitor) and 2.27 mpy (with inhibitor), corresponding to an inhibition efficiency of 89.89%. In the 3% NaCl medium, the corrosion rates were 11.3 mpy (without inhibitor) and 2.01 mpy (with inhibitor), resulting in an inhibition efficiency of 82.22%. These results indicate that tannin derived from salam leaves can effectively act as a corrosion inhibitor for aluminum in both hydrochloric acid and saline environments.

Keywords: aluminum, corrosion, inhibitor, tannin, salam leaves, syzygium polyanthum

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 2232-2254
doi: 10.17675/2305-6894-2025-14-4-26

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