Effect of Addition Tahongai Leaf Extract (Kleinhovia hospita Linn.) As Organic Inhibitor on 1040 AISI Steel

This research will study about corrosion inhibition by using tahongai leaf extract (Kleinhovia hospita Linn.) in a 3.5% NaCl environment. The inhibitor is extracted using maceration process from Tahongai leaf (Kleinhovia hospita Linn.). Testing of antioxidant activity using DPPH method gives result that antioxidant activity of tahongai leaf extract (Kleinhovia hospita Linn.) is strong antioxidant (96%) compared to vitamin C (98%), functional group test by FTIR method indicates that tahongai leaf extract (Kleinhovia hospita Linn.) contain flavonoid shown by O-H bond (3357.41 cm^-1), double bond C=C (164 3.36 cm^-1), C-H bond (2922.24 cm^-1, 1460.69 cm^-1, 1375.57 cm^-1), Efficiency of inhibition reach 99.9825% for addition of inhibitor with concentration 200 ppm and duration of immersion 20 days. This inhibition behavior is also supported by polarization measurements where the lowest corrosion rate of 8.3x10^-4 mm/year is obtained at the same concentration and immersion time.