Characterization of Papaya Leave's Extract in 3.56% NaCl Solution as Corrosion Inhibitor on Low Carbon Steel

Papaya leaf extract demonstrates promise as an organic corrosion inhibitor that can be used to reduce the rate of corrosion, particularly in corrosive environments such as the marine environment. The purpose of this study was to determine the best concentration of papaya leaf extract inhibitor (Carica papaya) that effectively reduces the corrosion rate of low carbon steel in a 3.56% NaCl solution. The maceration process was carried out for 24 h with 70% ethanol solvent with a solute: solvent ratio of 1:8 (w:v) at room temperature. Inhibitor extracts were analyzed qualitatively with the phytochemical FeCl3 method. The addition of FeCl3 was carried out on the inhibitor extract from papaya leaves. The change of the papaya leaf extract's colour from blackish brown to greenish black indicated the presence of tannin compounds. Corrosion testing was carried out with hot stream temperature setting at 45 °C to 55 °C and concentrations of inhibitor extracts at 300 ppm, 600 ppm and 900 ppm. The test was conducted for 36 h with a span of metal mass every 6 h. Corrosion rate calculation is done by weight loss method. The results demonstrated that papaya leaf extract inhibitors effectively reduced the corrosion rate in 3.56% NaCl solution, with the corrosion rate without inhibitor is 1.023 mmpy. Furthermore, inhibitor concentrations of 300 ppm, 600 ppm and 900 ppm corresponded to corrosion rates of 0.755 mmpy, 0.585 mmpy and 0.438 mmpy, respectively. The efficiency of papaya leaf inhibitor with inhibitor concentrations of 300 ppm, 600 ppm, 900 ppm rwas 26.19%; 42.85%; and 57.14%, respectively. The highest efficiency, with a value 57.14%was found in the inhibitor concentration of 900 ppm. In conclusion, Papaya leave’s extract as corrosion inhibitor was able to reduce corrosion rate from 1.023 mmpy into 0.438 mmpy with 57.14% of efficiency.